JP7261945B1 - Hole-transporting material, precursor for synthesizing hole-transporting material and method for producing hole-transporting material - Google Patents

Abstract

The present invention uses a perovskite crystal of lead methylammonium iodide (NH3CH3PbI3) as a solar absorber and spiro-OMeTAD as a hole transport material. Provided is a new hole-transporting material that provides sufficient photoelectric conversion efficiency and high durability even in the absence of such a material. It also provides a synthetic route via the precursor octabromo substituent for efficiently synthesizing such hole-transporting materials.

Description

TECHNICAL FIELD The present invention relates to a hole transport material that can be used in organic solar cells such as dye-sensitized solar cells. In particular, it relates to hole transport materials that can be used without dopants in perovskite solar cells and the like. It also relates to precursors for efficiently synthesizing such hole-transporting materials and methods of producing hole-transporting materials using such precursors.

Most of the solar cells in widespread use at present are silicon solar cells and compound solar cells. These solar cells are highly durable and exhibit high energy conversion efficiency (achieving 25%), but the raw material and manufacturing costs are high, and in the case of silicon-based solar cells, the silicon is thick and the panel is flexible. There were disadvantages such as restrictions on installation locations due to lack of flexibility.
Therefore, a lead halide-based perovskite solar cell was developed for the first time in 2009 (Non-Patent Document 1). A solar cell based on such an organic thin film material is excellent in terms of resource saving and can be manufactured in a large area, so it is excellent in terms of manufacturing cost.

Research into perovskite solar _cells has focused on lead methylammonium iodide ( _NH3CH3PbI3 ), _a brown compound obtained by mixing lead iodide ( _PbI2 ) and methylammonium iodide _{( CH3NH3I} ). ) is useful as a sensitizer for a dye-sensitized solar cell using a titanium oxide porous film.
A perovskite solar cell _uses a perovskite crystal of lead methylammonium iodide ( _NH3CH3PbI3 ) as a solar absorber, where an electron transport layer and photogenerated holes are used to collect photogenerated electrons and transport them to the anode _. to the cathode is joined.

Based on the construction materials and structures reported in the last few years, perovskite-based solar cells can be broadly classified into four types:
(a) A type in which an electron-transporting material is deposited on a transparent electrode and a photoactive porous material layer such as mesoporous TiO ₂ (mp-TiO ₂ ) is formed thereon to serve as a scaffold for perovskite crystals;
(b) A type in which an electron-transporting material is deposited on a transparent electrode and a photo-inactive porous material such as mesoporous Al ₂ O ₃ (mp-Al ₂ O ₃ ) is formed thereon to serve as a scaffold for perovskite crystals;
(c) A planar order structure type in which an electron transport material is deposited on a transparent electrode and a perovskite planar absorption layer is bonded thereon;
(d) A planar inverse structure type in which a hole-transporting material is deposited on a transparent electrode and a perovskite planar absorption layer is bonded thereon.

Currently, the highest performing perovskite solar cells employ mp- _TiO2 as a scaffold to form perovskite crystals used as light absorbers. The mp- _TiO2 provides a large-area scaffold for homogeneous perovskite infiltration, collecting photogenerated electrons and transferring them to a fluorine-doped tin oxide (FTO) electrode as an electron transport material (electron). -transporting material; ETM) layer. First, such an ETM layer is formed on the FTO substrate, on which the mp- _TiO2 layer is formed. Using this mp-TiO ₂ layer as a scaffold, a perovskite crystal is generated. Al ₂ O ₃ and ZrO ₂ can also be used as the mesoporous oxide. A hole transport layer is formed thereon, and a cathode electrode of Au or Ag is joined.

When mesoporous oxide is used as a perovskite scaffold or dense TiO ₂ (c-TiO ₂ ) layer is used as an electron transport layer, the processing temperature is usually higher than 400°C, so expensive FTO is used for the anode transparent substrate. be done.
As a perovskite, lead methylammonium iodide ( _NH3CH3PbI3 ; _MAPI ) can be used, and as a hole-transporting material ( _HTM ) for MAPI, 2,2',7,7 '-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9 ,9'-spirobifluorene; spiro-OMeTAD) can be used.

When light is incident from the transparent electrode side of a solar cell with such a structure (e.g., FTO/c-TiO ₂ /meso-TiO ₂ -MAPI/MAPI/spiro-OMeTAD/Au), the perovskite light absorber Holes are generated, electrons are transported through the electron transport layer to the transparent electrode, and holes are transported through the hole transport layer to the cathode. A solar cell with such a structure is a nip (forward) photovoltaic device, like a solid-state dye-sensitized solar cell.

On the other hand, a structure in which a hole transport layer is formed on a transparent electrode, a perovskite light absorber layer is formed thereon, and an electron transport layer is further formed thereon (for example, FTO/PEDOT:PSS/MAPI _{3- x} Cl _x /PCBM/TiO _x /Al) solar cells are pin-type (reverse) photovoltaic devices.

The above perovskite crystals are easy to fabricate, making it possible to reduce manufacturing costs compared to conventional solar cells. Furthermore, flexible and lightweight solar cells can be realized, making it possible to install them in various locations. rice field. While perovskite solar cells have these advantages, they also have a high conversion efficiency (21.6%) comparable to silicon-based solar cells and compound-based solar cells, and a high voltage output of 1.15 V or higher. Realized.
For this reason, perovskite solar cells have received the most attention in the world and have been the subject of many researchers.

WO2019/181940 Japanese Patent Publication No. 2006-502960 JP-A-7-118185 Japanese Patent Publication No. 2010-538051

Kojima, A. et al., J. Am. Chem. Soc. 2009, 131, 6050-6051 Zhao, H. et al., Chem. Sci. 2016, 7, 5007-5012 Calio, L. et al., Angew. Chem. Int. Ed. 2016, 55, 14522-14545 Wu, R. et al., J. Org. Chem., 1996, 61, 6906-6921

で示されるスピロビフルオレン骨格を有し、式中、４つのＲは、同一で、式（ＩＩ）：

（式中、Meはメチル基を示し、記号＊は結合点を意味する。）で示されるN,N-ジ-p-メトキシフェニルアミノ基である。Perovskite solar cells, which are currently mainstream, use perovskite crystals of lead methylammonium iodide (NH ₃ CH ₃ PbI ₃ ; MAPI) as a solar absorber. In order to achieve high photovoltaic conversion efficiency (PCE) in perovskite solar cells, hole transport is required due to having good glass transition temperature; reasonable solubility; moderate ionization potential; low visible light absorption; Currently, 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) is often used as a material. 2,2',7,7'-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) has the formula (I):

has a spirobifluorene skeleton represented by the formula (II):

(In the formula, Me represents a methyl group, and the symbol * means a bonding point.).

で示すことができる。Thus, the overall structure of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) is represented by formula (Ia):

can be shown as

When spiro-OMeTAD is used as a hole transport layer, additives such as lithium bis(trifluoromethane)sulfonimide (LiTFSI) and 4-tert-butyl pyridine (TBP), i.e., dopants, are added. Added. Pure spiro-OMeTAD has relatively low hole mobility and conductivity, so the addition of these dopants modulates these electronic properties.

However, since LiTFSI and TBP dopants are hygroscopic and volatile, they accelerate deterioration of the battery, and they are not covalently bonded to HTM, so they easily diffuse. Moreover, the cost also increases.
Other additives and dopants include FK209 (tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tris[bis(trifluoromethane)sulfonimide]), F4TCNQ (tetra fluorotetracyanoquinodimethane), N(PhBr) _{3SbCl6 ,} etc., but none of them show satisfactory solar cell properties.

For example, Patent Document 1 describes a conventional solar cell in which MAPI is used as an organic/inorganic perovskite, spiro-OMeTAD is used as a hole transport layer, and a TBP dopant is added. Disclosed is a technique for suppressing deterioration of a photoelectric conversion layer due to transmission through an insulating layer.

Accordingly, the present invention provides a perovskite solar cell using perovskite crystals of lead methylammonium iodide (NH ₃ CH ₃ PbI ₃ ) as a sunlight absorber and spiro-OMeTAD as a hole transport material. The challenge is to provide a new hole-transporting material to replace spiro-OMeTAD, which is dopant-free for improved stability, yet has sufficient photoelectric conversion efficiency and high durability without the need for a special insulating layer. do.

In addition, the present inventors have found a synthetic route for efficiently synthesizing a hole-transporting material, particularly a compound containing an N,N-di-p-substituted phenylamino group such as spiro-OMeTAD, and a method for synthesizing such a compound. The next task was to provide useful precursors for the synthesis of these compounds.

In view of the above problems, the present inventors have conducted extensive research, and found that the formula (II) shows
The highest occupied orbital level (E _HOMO ) is adjusted by changing the type and substitution position of the substituent on the phenyl ring of the N,N-di-substituted phenylamino group from "p-position substitution of methoxy group". , which can control the photoelectric conversion efficiency (PCE).

In particular, among the above hole-transporting materials, derivatives having an N-substituted amino group or an N,N-disubstituted amino group at the p-position of the phenyl group as the N,N-di-substituted phenylamino group can be used even if they are dopant-free. It was found that the photoelectric conversion efficiency was comparable to that of the dopant addition. Based on this finding, furthermore, the type of substituents at the p- _position and the o-position or It is required to explore further types of substituents to be introduced at the m-position.

Then, the present inventors have found novel octabromo compounds in which the p-position substituents of the phenyl groups on the two phenyl rings in the N,N-bis(p-substituted phenyl)amino groups in the spirobifluoroene compounds are bromine. We have found that the substituted compounds are useful as precursors for hole transport materials. That is, the present inventors used 2,2',7,7'-tetrakis(N,N-di-p-bromophenylamine)-9,9'-spirobifluorene as a precursor and , with a desired amino group, an N,N-di-substituted phenylamino group having an N-substituted amino group or an N,N-disubstituted amino group, to obtain a 2,2' having a desired substituent. ,7,7'-Tetrakis(N,N-di-p-substituted phenylamine)-9,9'-spirobifluorene was synthesized efficiently.

〔式中、
４つのＲ^０は、同一で、式（ＩＶ）：

｛式中、
Ｒ^１からＲ^１０のうち少なくとも１つは、独立して、式（Ｖ）：

［式中、
Ｒ^１１およびＲ^１２は、独立して、水素原子、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、置換もしくは非置換のフェニル基、窒素含有ヘテロ芳香族基、もしくは式（ＶＩ）：

（式中、
Ｒ^１３は、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、アミノ基、もしくは置換もしくは非置換のフェニル基で置換されたN-置換もしくはN,N-二置換アミノ基である。）で表されるアミド結合を有する有機基であって、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、もしくは前記フェニル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、置換もしくは非置換の５～８員のヘテロシクロアルキル基を形成し、ここに、前記ヘテロシクロアルキル基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記５～８員のヘテロシクロアルキル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され、もしくは、いずれか２辺に置換もしくは非置換のベンゼン環が縮合していてもよく；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、単環もしくは縮合環からなる置換もしくは非置換のヘテロ芳香族環基を形成し、ここに、前記ヘテロ芳香族環基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記ヘテロ芳香族環が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。］で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基であり、
Ｒ^１からＲ^１０のうち、上記式（Ｖ）で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基ではない置換基は、独立して、水素原子、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、もしくは窒素含有芳香族環基であり、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、もしくは前記窒素含有芳香族環基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基からなる群から選択され、記号＊は結合点を意味する。｝で示されるN,N-ジ-置換フェニルアミノ基である。〕で示される正孔輸送材料が提供される。More particularly, in the first aspect of the invention, formula (III):

[In the formula,
The four R ⁰ are the same and have formula (IV):

{In the formula,
At least one of R ¹ through R ¹⁰ is independently of formula (V):

[In the formula,
R ¹¹ and R ¹² are independently a hydrogen atom, a substituted or unsubstituted linear or branched C _1-4 alkyl group, a substituted or unsubstituted phenyl group, a nitrogen-containing heteroaromatic group, or the formula (VI):

(In the formula,
R ¹³ is a substituted or unsubstituted linear or branched C _1-4 alkyl group, a substituted or unsubstituted linear or branched C _1-4 alkoxy group, an amino group, or a substituted or unsubstituted is an N-substituted or N,N-disubstituted amino group substituted with a phenyl group of ) is an organic group having an amide bond represented by
If the linear or branched C _1-4 alkyl group, the linear or branched C _1-4 alkoxy group, or the phenyl group is substituted, the substituent is F , Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a substituted or unsubstituted 5- to 8-membered heterocycloalkyl group, wherein said heterocycloalkyl group is said to be In addition to the bonding nitrogen atom, the ring may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom,
If said 5- to 8-membered heterocycloalkyl group is substituted, the substituent is a halogen atom selected from F, Cl, Br and I, hydroxyl group, carbonyl group, nitro group, cyano group , a sulfonyl group, or any two sides may be fused with a substituted or unsubstituted benzene ring; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a substituted or unsubstituted heteroaromatic ring group consisting of a single ring or a condensed ring, wherein the heteroaromatic ring group is , in addition to the nitrogen atom to which they are attached, may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom in the ring,
If the heteroaromatic ring is substituted, the substituents consist of halogen atoms selected from F, Cl, Br and I, hydroxyl groups, carbonyl groups, nitro groups, cyano groups, sulfonyl groups. selected from the group. ], an N-substituted amino group or an N,N-disubstituted amino group,
Among R ¹ to R ¹⁰ , the substituents other than the amino group, N-substituted amino group or N,N-disubstituted amino group represented by the above formula (V) are independently a hydrogen atom, F, Cl, halogen atom selected from Br and I, hydroxyl group, carbonyl group, nitro group, cyano group, sulfonyl group, trifluoromethyl group, substituted or unsubstituted linear or branched C _1-4 alkyl group, substituted or an unsubstituted linear or branched C _1-4 alkoxy group, or a nitrogen-containing aromatic ring group,
If the linear or branched C _1-4 alkyl group, the linear or branched C _1-4 alkoxy group, or the nitrogen-containing aromatic ring group is substituted, the substitution The group is selected from the group consisting of a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group, a trifluoromethyl group, and the symbol * means the point of attachment. do. } is an N,N-di-substituted phenylamino group. ] is provided.

In the second aspect of the present invention, a transparent electrode, an electron transport layer, a mesoporous _TiO2 layer, a perovskite layer using the mesoporous _TiO2 layer as a scaffold, a hole transport layer and a metal electrode are joined in this order. There is provided a perovskite solar cell with a nip structure, wherein said hole transport layer comprises the hole transport material of the first aspect of the present invention.

In one embodiment of the second aspect of the present invention, the perovskite has the formula ABX ₃ , where A is methylammonium (CH ₃ NH ₃ ⁺ ) and formamidinium (HC(NH ₂ ) ₂ ⁺ ), or at least one monovalent alkali metal ion selected from lithium (Li ⁺ ), sodium (Na ⁺ ), potassium (K ⁺ ), rubidium (Rb ⁺ ) and cesium (Cs ⁺ ) is a cation, B is a divalent cation of at least one metal element selected from magnesium (Mg), tin (Sn) and lead (Pb), and X is chlorine (Cl) and bromine (Br) and iodine (I), and the perovskite is MAPbI ₃ (lead methylammonium iodide), Cs _0.05 (FA _0.85 MA _0.15 ) _0.95 Pb(I _0.89 Br _0.11 ) ₃ , or FAPbI ₃ ( lead formamidinium iodide).

In one embodiment of the second aspect of the present invention, the hole-transporting layer consists solely of said hole-transporting material, with additives used to modulate electronic properties such as hole mobility and conductivity, e.g. , lithium bis(trifluoromethane)sulfonimide (LiTFSI), 4-tert-butyl pyridine (TBP), FK209 (tris(2-(1H-pyrazol-1-yl)-4-tert- It does not contain dopants selected from butylpyridine)cobalt(III)tris[bis(trifluoromethane)sulfonimide]), F4TCNQ (tetrafluorotetracyanoquinodimethane), N( _PhBr ) _3SbCl6 .

In a third aspect of the present invention, there is provided a method of manufacturing the perovskite solar cell of the second aspect.
In the perovskite solar cell according to the present invention, a step of forming an electron transport layer by forming an amorphous dense titanium oxide film on the fluorine-doped tin oxide coat of the fluorine-doped tin oxide-coated transparent electrode;
forming a mesoporous titanium oxide layer on the electron transport layer;
forming a perovskite layer on the mesoporous titanium oxide layer by applying a perovskite solution;
Manufactured using a manufacturing method comprising forming a hole-transporting layer on the perovskite layer by applying a solution of a hole-transporting material.

〔式中、
４つのＲ^２０は、同一で、式（ＶＩＩＩ）：

｛式中、
Ｒ^２１、Ｒ^２２、Ｒ^２４、Ｒ^２５、Ｒ^２６、Ｒ^２７、Ｒ^２９およびＲ^３０は、独立して、水素原子、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは窒素含有芳香族環基であり、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは前記窒素含有芳香族環基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。）で示されるN,N-ジ-(p-ブロモ置換フェニル)アミノ基であり、
Ｒ^２３およびＲ^２８は、独立して、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、置換もしくは非置換の芳香族環（ここに、前記芳香族環は、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記芳香族環が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。）、もしくは式（ＩＸ）：

［式中、
Ｒ^３１およびＲ^３２は、独立して、水素原子、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換のフェニル基、窒素含有ヘテロ芳香族基、もしくは、式（Ｘ）：

（式中、
Ｒ^３３は、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、アミノ基、もしくは置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは置換もしくは非置換のフェニル基で置換されたN-置換もしくはN,N-二置換アミノ基である。）で示されるアミド結合を有する有機基であって、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは前記フェニル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され；または、
Ｒ^３１およびＲ^３２は、それらが結合する窒素原子と一緒になって、置換もしくは非置換の５～８員のヘテロシクロアルキル基を形成し、ここに、前記ヘテロシクロアルキル基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記５～８員のヘテロシクロアルキル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され、もしくは、いずれか２辺に置換もしくは非置換のベンゼン環が縮合していてもよく；または、
Ｒ^３１およびＲ^３２は、それらが結合する窒素原子と一緒になって、単環若しくは縮合環からなる置換もしくは非置換のヘテロ芳香族環基を形成し、ここに、前記ヘテロ芳香族環基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記ヘテロ芳香族環が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。］で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基である。｝で示されるN,N-ジ-(p-置換フェニル)アミノ基であり、記号＊は結合点を意味する。〕で示される2,2’,7,7’-テトラキス(N,N-ジ-p-置換フェニルアミン)-9,9’-スピロビフルオレンが、ペロブスカイト太陽電池の特性を向上させることを確認した。Furthermore, the present inventors found that among the above hole-transporting materials, formula (VII):

[In the formula,
The four R ²⁰ are the same and have the formula (VIII):

{In the formula,
^R21 , ^R22 , ^R24 , ^R25 , ^R26 , ^R27 , ^R29 and ^R30 are independently a hydrogen atom, a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl a nitro group, a cyano group, a sulfonyl group, a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, or a nitrogen-containing aromatic ring group,
If the linear or branched C _1-3 alkyl group, the linear or branched C _1-3 alkoxy group, or the nitrogen-containing aromatic ring group is substituted, the substitution The groups are selected from the group consisting of halogen atoms selected from F, Cl, Br and I, hydroxyl groups, carbonyl groups, nitro groups, cyano groups, sulfonyl groups. ) is an N,N-di-(p-bromo-substituted phenyl) amino group represented by
R ²³ and R ²⁸ are independently substituted or unsubstituted linear or branched C _1-3 alkyl groups, substituted or unsubstituted linear or branched C _1-3 alkoxy groups, substituted or an unsubstituted aromatic ring (wherein said aromatic ring may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom in the ring,
If the aromatic ring is substituted, the substituent is the group consisting of a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group. is selected from ), or formula (IX):

[In the formula,
R ³¹ and R ³² are independently a hydrogen atom, a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted phenyl group, a nitrogen-containing heteroaromatic group, or Formula (X):

(In the formula,
R ³³ is a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, an amino group, or a substituted or unsubstituted A linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, or N-substituted or substituted with a substituted or unsubstituted phenyl group It is an N,N-disubstituted amino group. ) is an organic group having an amide bond represented by
If the linear or branched C _1-3 alkyl group, the linear or branched C _1-3 alkoxy group, or the phenyl group is substituted, the substituent is F , Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group; or
R ³¹ and R ³² together with the nitrogen atom to which they are attached form a substituted or unsubstituted 5- to 8-membered heterocycloalkyl group, wherein said heterocycloalkyl group is said to be In addition to the bonding nitrogen atom, the ring may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom,
If said 5- to 8-membered heterocycloalkyl group is substituted, the substituent is a halogen atom selected from F, Cl, Br and I, hydroxyl group, carbonyl group, nitro group, cyano group , a sulfonyl group, or any two sides may be fused with a substituted or unsubstituted benzene ring; or
R ³¹ and R ³² together with the nitrogen atom to which they are attached form a substituted or unsubstituted heteroaromatic ring group consisting of a single ring or condensed ring, wherein said heteroaromatic ring group is , in addition to the nitrogen atom to which they are attached, may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom in the ring,
If the heteroaromatic ring is substituted, the substituents consist of halogen atoms selected from F, Cl, Br and I, hydroxyl groups, carbonyl groups, nitro groups, cyano groups, sulfonyl groups. selected from the group. ], an N-substituted amino group or an N,N-disubstituted amino group. }, and the symbol * means the point of attachment. ] shows that 2,2',7,7'-tetrakis(N,N-di-p-substituted phenylamine)-9,9'-spirobifluorene improves the properties of perovskite solar cells. bottom.

［式中、
４つのＲ^３４は、同一で、式（ＸＩＩ）：

（式中、
Brは臭素原子を表し、
Ｒ^２１、Ｒ^２２、Ｒ^２４、Ｒ^２５、Ｒ^２６、Ｒ^２７、Ｒ^２９およびＲ^３０は、独立して、水素原子、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは窒素含有芳香族環基であり、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは前記窒素含有芳香族環基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され、記号＊は結合点を意味する。）で示されるN,N-ジ-(p-ブロモ置換フェニル)アミノ基である。］で示される2,2’,7,7’-テトラキス(N,N-ジ-p-ブロモ置換フェニルアミン)-9,9’-スピロビフルオレン（以下、簡便に「オクタブロモ置換体」ということもある。）を開発した。Therefore, in order to efficiently synthesize a wide variety of hole-transporting materials having the above N,N-di-(p-substituted phenyl)amino group, the present inventors, in the fourth aspect of the present invention, As a precursor of the hole-transporting material, formula (XI):

[In the formula,
The four R ³⁴ are the same and have formula (XII):

(In the formula,
Br represents a bromine atom,
^R21 , ^R22 , ^R24 , ^R25 , ^R26 , ^R27 , ^R29 and ^R30 are independently a hydrogen atom, a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl a nitro group, a cyano group, a sulfonyl group, a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, or a nitrogen-containing aromatic ring group,
If the linear or branched C _1-3 alkyl group, the linear or branched C _1-3 alkoxy group, or the nitrogen-containing aromatic ring group is substituted, the substitution The group is selected from the group consisting of halogen atoms selected from F, Cl, Br and I, hydroxyl groups, carbonyl groups, nitro groups, cyano groups, sulfonyl groups, and the symbol * means the point of attachment. ) is an N,N-di-(p-bromo-substituted phenyl)amino group. ] 2,2',7,7'-Tetrakis(N,N-di-p-bromo-substituted phenylamine)-9,9'-spirobifluorene (hereinafter simply referred to as "octabromo-substituted product" ) was developed.

［式中
Ｒ^３１およびＲ^３２は、独立して、水素原子、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換のフェニル基、窒素含有ヘテロ芳香族基、もしくは、式（ＸＩＶ）：

（式中、
Ｒ^３３は、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、アミノ基、もしくは置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは置換もしくは非置換のフェニル基で置換されたN-置換もしくはN,N-二置換アミノ基であり、記号＊は結合点を意味する。）で示されるアミド結合を有する有機基であって、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～３アルコキシ基、もしくは前記フェニル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され；または、
Ｒ^３１およびＲ^３２は、それらが結合する窒素原子と一緒になって、置換もしくは非置換の５～８員のヘテロシクロアルキル基を形成し、ここに、前記ヘテロシクロアルキル基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記５～８員のヘテロシクロアルキル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択され、もしくは、いずれか２辺に置換もしくは非置換のベンゼン環が縮合していてもよく；または、
Ｒ^３１およびＲ^３２は、それらが結合する窒素原子と一緒になって、単環若しくは縮合環からなる置換もしくは非置換のヘテロ芳香族環基を形成し、ここに、前記ヘテロ芳香族環基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記ヘテロ芳香族環が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。］で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基である。｝で示されるN,N-ジ-置換フェニルアミノ基と、
を反応させるステップを含む製造方法により、式（ＶＩＩ）で示されるで示される2,2’,7,7’-テトラキス(N,N-ジ-p-置換フェニルアミン)-9,9’-スピロビフルオレンを効率よく合成する。Also, in the fifth aspect of the present invention, at least an octabromo-substituted compound represented by formula (XI);
substituted or unsubstituted linear or branched C _1-3 alkyl, substituted or unsubstituted linear or branched C _1-3 alkoxy group, substituted or unsubstituted aromatic ring (here, the The aromatic ring may contain heteroatoms in the ring selected from the group consisting of oxygen, nitrogen and sulfur atoms, and if said aromatic ring is substituted, the substituents are , a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group) or formula (XIII):

[wherein R ³¹ and R ³² are independently a hydrogen atom, a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted phenyl group, a nitrogen-containing heteroaromatic group, or formula (XIV):

(In the formula,
R ³³ is a substituted or unsubstituted linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, an amino group, or a substituted or unsubstituted A linear or branched C _1-3 alkyl group, a substituted or unsubstituted linear or branched C _1-3 alkoxy group, or N-substituted or substituted with a substituted or unsubstituted phenyl group It is an N,N-disubstituted amino group, and the symbol * means the point of attachment. ) is an organic group having an amide bond represented by
If the linear or branched C _1-3 alkyl group, the linear or branched C _1-3 alkoxy group, or the phenyl group is substituted, the substituent is F , Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group; or
R ³¹ and R ³² together with the nitrogen atom to which they are attached form a substituted or unsubstituted 5- to 8-membered heterocycloalkyl group, wherein said heterocycloalkyl group is said to be In addition to the bonding nitrogen atom, the ring may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom,
If said 5- to 8-membered heterocycloalkyl group is substituted, the substituent is a halogen atom selected from F, Cl, Br and I, hydroxyl group, carbonyl group, nitro group, cyano group , a sulfonyl group, or any two sides may be fused with a substituted or unsubstituted benzene ring; or
R ³¹ and R ³² together with the nitrogen atom to which they are attached form a substituted or unsubstituted heteroaromatic ring group consisting of a single ring or condensed ring, wherein said heteroaromatic ring group is , in addition to the nitrogen atom to which they are attached, may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom in the ring,
If the heteroaromatic ring is substituted, the substituents consist of halogen atoms selected from F, Cl, Br and I, hydroxyl groups, carbonyl groups, nitro groups, cyano groups, sulfonyl groups. selected from the group. ], an N-substituted amino group or an N,N-disubstituted amino group. } and an N,N-di-substituted phenylamino group represented by
2,2',7,7'-Tetrakis(N,N-di-p-substituted phenylamine)-9,9'- represented by formula (VII) To efficiently synthesize spirobifluorene.

で示される2,2’,7,7’-テトラブロモ-9,9’-スピロビフルオレンと、所望する置換基を有するN,N-ジ-置換フェニルアミンとを反応させることで得ることができる。Octabromo substituents of formula (XI) that are useful precursors according to the invention are, for example, of formula (XV):

It can be obtained by reacting 2,2',7,7'-tetrabromo-9,9'-spirobifluorene represented by with N,N-di-substituted phenylamine having a desired substituent. .

（式中、
Ｒ^２１、Ｒ^２２、Ｒ^２４、Ｒ^２５、Ｒ^２６、Ｒ^２７、Ｒ^２９およびＲ^３０は、独立して、水素原子、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、置換もしくは非置換のＣ_１～３アルキル基、置換もしくは非置換のＣ_１～３アルコキシ基、もしくは窒素含有芳香族環基であり、
もし、前記Ｃ_１～３アルキル基、前記Ｃ_１～３アルコキシ基、もしくは前記窒素含有芳香族環基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基からなる群から選択される。）で示される。N,N-di-(substituted phenyl)amines with desired substitution may also be represented by formula (XVI):

(In the formula,
^R21 , ^R22 , ^R24 , ^R25 , ^R26 , ^R27 , ^R29 and ^R30 are independently a hydrogen atom, a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl a nitro group, a cyano group, a sulfonyl group, a substituted or unsubstituted C _1-3 alkyl group, a substituted or unsubstituted C _1-3 alkoxy group, or a nitrogen-containing aromatic ring group;
If said C _1-3 alkyl group, said C _1-3 alkoxy group, or said nitrogen-containing aromatic ring group is substituted, the substituents are selected from F, Cl, Br and I It is selected from the group consisting of halogen, hydroxyl group, carbonyl group, nitro group, cyano group, sulfonyl group. ).

That is, 2,2',7,7'-tetrabromo-9,9'-spirobifluorene represented by formula (XV) is reacted with N,N-di-substituted phenylamine represented by formula (XVI). In 2,2',7,7'-tetrakis(N,N-di-substituted phenylamine)-9,9'-spirobifluorene obtained by Bromination of the p-position on the phenyl ring provides the octabromo substitution of formula (XI).

で示される2,2’,7,7’-テトラキス(N,N-ジ-p-ブロモフェニルアミン)-9,9’-スピロビフルオレンである。In such 2,2′,7,7′-tetrakis(N,N-di-p-bromosubstituted phenylamine)-9,9′-spirobifluorenes, R ²¹ , R ²² , R ²⁴ , R ²⁵ , R ²⁶ , R ²⁷ , R ²⁹ and R ³⁰ are all hydrogen atoms, formula (XIa):

2,2',7,7'-Tetrakis(N,N-di-p-bromophenylamine)-9,9'-spirobifluorene represented by

In perovskite solar cells using perovskite crystals of lead methylammonium iodide (NH ₃ CH ₃ PbI ₃ ) as a solar absorber, the hole-transporting material of the present invention can be used as a dopant to destabilize the photoelectric properties of the solar cell. It is possible to provide a perovskite solar cell having sufficient photoelectric conversion efficiency and high durability even in the absence of .
Furthermore, a new synthetic route using the precursors developed in the present invention would improve the efficiency of synthesizing hole-transporting materials containing N,N-di-p-substituted phenylamino groups.

Schematic cross-section of a nip-type (forward-oriented) structure solar cell employing mp-TiO ₂ as a scaffold to form perovskite crystals. Fig. 2 shows a comparison of change in conversion efficiency over time with and without a dopant in a solar cell using the hole-transporting material of the present invention.

The present invention is a hole-transporting material with properties exceeding spiro-OMeTAD, especially in a nip-type (forward-type) structure solar cell (Fig. 1) that employs mp- _TiO2 as a scaffold to form perovskite crystals. I will provide a.

Various spiro-OMeTAD analogs with different types and positions of substituents on the phenyl ring of the N,N-disubstituted phenylamino group of spiro-OMeTAD to adjust the highest occupied molecular orbital level (E _HOMO ). We fabricated perovskite solar cells using a body as HTM, and measured the photoelectric conversion efficiency (PCE) with and without dopants such as LiTFSI and TBP.

[Hole transport material]
The hole-transporting material (HTM) represented by formula (III) includes the conventional hole-transporting material spiro-OMeTAD as a control. In the present invention, the methoxy group, which is the substituent on the phenyl ring of the N,N-di-(p-methoxyphenyl)amino group of spiro-OMeTAD, can be replaced by a dimethylamino group, an ethylmethylamino group, a methylpropylamino group, a methyl isopropylamino group, methylbutylamino group, methylisobutylamino group, methyltert-butylamino group, methylsec-butylamino group, diethylamino group, ethylpropylamino group, ethylisopropylamino group, ethylbutylamino group, ethylisobutylamino group , ethyl tert-butylamino group, ethyl sec-butylamino group, dipropylamino group, diisopropylamino group, propylbutylamino group, propylisobutylamino group, propyl tert-butylamino group, propyl sec-butylamino group, isopropylbutyl amino group, isopropyl isobutylamino group, isopropyl tert-butylamino group, isopropyl sec-butylamino group, dibutylamino group, butyl isobutylamino group, butyl tert-butylamino group, butyl sec-butylamino group, diisobutylamino group, isobutyl N,N-dialkyl-substituted amino group selected from the group consisting of tert-butylamino group, isobutyl sec-butylamino group, di-tert-butylamino group, tert-butyl sec-butylamino group or di-sec-butylamino group or one or more selected from the group consisting of a hydroxyl group, a C _1-4 alkoxy group, a halogen group, a nitro group, and a cyano group. selected from the group consisting of substituted or unsubstituted pyrrolidinyl, pyrazolidinyl, oxazolidinyl, thiazolidinyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, azepinyl, thiazepinyl and azocanyl groups HTMs containing N,N-di-(p-substituted phenyl)amino groups modified to N,N-di-(substituted heterocycloalkyl)amino groups modified to any of the organic groups are effective. Furthermore, the m-position of the phenyl ring of the N,N-di-(p-substituted phenyl)amino group is substituted with a voltage-attracting substituent selected from the group consisting of a nitro group and a cyano group. HTMs containing di-(p,m-di-substituted phenyl)amino groups are effective.

〔式中、
４つのＲ^０は、同一で、式（ＩＶ）：

｛式中、
Ｒ^１からＲ^１０のうち少なくとも１つは、独立して、式（Ｖ）：

［式中、
Ｒ^１１およびＲ^１２は、独立して、水素原子、メチル基、エチル基、n-プロピル基、iso-プロピル基、n-ブチル基、iso-ブチル基、sec-ブチル基、tert-ブチル基、フェニル基、2-ピリジル基、3-ピリジル基、4-ピリジル基、もしくは、式（ＶＩ）：

（式中、
Ｒ^１３は、メチル基、エチル基、n-プロピル基、iso-プロピル基、n-ブチル基、iso-ブチル基、sec-ブチル基、tert-ブチル基、メトキシ基、エトキシ基、n-プロポキシ基、iso-プロポキシ基、n-ブトキシ基、iso-ブトキシ基、sec-ブトキシ基、tert-ブトキシ基、N-モノフェニルアミノ基、N,N-ジフェニルアミノ基であるか；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、ピペリジノ基、モルホリノ基もしくはチオモルホリノ基を形成し、；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、ピロリル基、2,5-ジメチルピロリル基、ピリジニル基、カルバゾリル基、4,4’-ジメトキシカルバゾリル基を形成する。］で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基であり、
Ｒ^１からＲ^１０のうち、上記式（Ｖ）で示されるN-置換アミノ基もしくはN,N-二置換アミノ基ではない置換基は、水素原子、フッ素原子、塩素原子、臭素原子、ヨウ素原子、メチル基、エチル基、n-プロピル基、iso-プロピル基、n-ブチル基、iso-ブチル基、sec-ブチル基、tert-ブチル基、メトキシ基、エトキシ基、n-プロポキシ基、iso-プロポキシ基、n-ブトキシ基、iso-ブトキシ基、sec-ブトキシ基、tert-ブトキシ基、ヒドロキシル基、カルボニル基、ニトロ基、スルホニル基、シアノ基、2-ピロリル基、3-ピロリル基、2-ピリジル基、3-ピリジル基、4-ピリジル基もしくはトリフルオロメチル基であり、記号＊は結合点を意味する。｝で示されるN,N-ジ-置換フェニルアミノ基である。〕で示される。In one embodiment, the hole transport material (HTM) of the present invention has formula (III):

[In the formula,
The four R ⁰ are the same and have formula (IV):

{In the formula,
At least one of R ¹ through R ¹⁰ is independently of formula (V):

[In the formula,
R ¹¹ and R ¹² are independently hydrogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, phenyl group, 2-pyridyl group, 3-pyridyl group, 4-pyridyl group, or formula (VI):

(In the formula,
R ¹³ is a methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, methoxy group, ethoxy group, n-propoxy group , iso-propoxy, n-butoxy, iso-butoxy, sec-butoxy, tert-butoxy, N-monophenylamino, N,N-diphenylamino; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a piperidino group, a morpholino group or a thiomorpholino group; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a pyrrolyl group, 2,5-dimethylpyrrolyl group, pyridinyl group, carbazolyl group, 4,4'-dimethoxycarbazolyl group . ], an N-substituted amino group or an N,N-disubstituted amino group,
Among R ¹ to R ¹⁰ , the substituent other than the N-substituted amino group or the N,N-disubstituted amino group represented by the above formula (V) is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. , methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, methoxy group, ethoxy group, n-propoxy group, iso- Propoxy group, n-butoxy group, iso-butoxy group, sec-butoxy group, tert-butoxy group, hydroxyl group, carbonyl group, nitro group, sulfonyl group, cyano group, 2-pyrrolyl group, 3-pyrrolyl group, 2- It is a pyridyl group, 3-pyridyl group, 4-pyridyl group or trifluoromethyl group, and the symbol * means a bonding point. } is an N,N-di-substituted phenylamino group. ].

For example, Figure 7 of Non-Patent Document 3 includes several perovskites including lead methylammonium iodide ( _{NH3CH3PbI3 ; MAPbI3} : equivalent to MAPI in this specification ₎ and spiro-OMeTAD. A schematic diagram comparing the energy levels of several HTMs is depicted, and Tables 2 and 3 of Non-Patent Document 3 show physical properties such as PCE [%] and HOMO [eV] of each material measured in the solid state. Values are disclosed.
In the present invention, the physical property values of each material are discussed in terms of values measured in a solution state, so it is necessary to convert the physical property values described in Non-Patent Document 3 into values measured in a solution state. In Non-Patent Document 3, the highest occupied orbital level (HOMO level) of spiro-OMeTAD measured in a solid state was −5.22 eV. On the other hand, in the present invention, as shown in the section <Measurement method>, the highest occupied orbital level (E _HOMO ) of spiro-OMeTAD (hole transport material 1) measured in a solution state is as shown in Table 1. , was -4.81 eV.
Therefore, the value obtained by shifting the value of the HOMO level of HTM disclosed in Non-Patent Document 3 to the +0.4 eV shallow side is assumed to be the highest occupied molecular orbital level (E _HOMO ) measured in the solution state.

Then, the work functions corresponding to the HOMO values of the three perovskites are converted to -5.00, -5.03, and -5.25 eV, respectively. A slightly shallower HOMO level of HTM is required for hole transfer from perovskite to HTM. Therefore, depending on the type of perovskite used in combination, for example, when used with MAPI, the highest occupied molecular orbital level (E _HOMO ) of the HTM of the present invention is considered suitable, for example, up to about -4.85 eV.
Next, looking at the correlation between the HOMO level of HTM and PCE in Tables 2 and 3 of Non-Patent Document 3, PCE tended to improve when the HOMO level of the solution conversion value was deeper than -4.60 eV. .

［式中、
４つのＲ^０は、同一で、例えば、下式：

からなる群から選択されるN,N-ジ-置換フェニルアミノ基である。］で示されるスピロビフロオレン化合物が好ましい。また、式（ＩＶ）中、Ｒ^３およびＲ^８のうち少なくともひとつが、式（Ｖ）で示されるアミノ基、N-置換アミノ基またはN,N-二置換アミノ基であることが、より好ましい。すなわち、本発明のHTMは、式（ＩＩＩ）中、４つのＲ^０は、同一で、例えば、下式：

からなる群から選択されるN,N-ジ-p-置換フェニルアミノ基である。］で示されるスピロビフロオレン化合物である。Therefore, the HTM of the present invention, more specifically, was dissolved in a 0.1 M tetraethylammonium perchlorate (TEAP) supporting electrolyte solution (methylene chloride) and analyzed using an electrochemical analyzer (ALS/CH Instruments 610B) for DPV (Differential pulse voltammetry), the highest occupied molecular orbital level (E _HOMO ) is preferably -4.60 eV or less when the reference substance ferrocene is measured at -4.80 eV. For example, formula (III):

[In the formula,
The four R ⁰ are the same, for example:

N,N-di-substituted phenylamino groups selected from the group consisting of ] is preferred. Further, in formula (IV), at least one of R ³ and R ⁸ is more preferably an amino group represented by formula (V), an N-substituted amino group, or an N,N-disubstituted amino group. . That is, the HTM of the present invention has the formula (III) in which the four R ⁰ are the same, such as the following formula:

an N,N-di-p-substituted phenylamino group selected from the group consisting of ] is a spirobifluoroene compound represented by

An example of using a spirobifluoroene compound in which R ⁰ in formula (III) is an N,N-di-(p-dimethylaminophenyl)amino group in a pin type (reverse type) solar cell (Non-Patent Document 2 ), the nip-type (forward type) solar cell of the present invention exhibits high photoelectric conversion efficiency even when the above spirobifluoroene compound is used in the dopant-free hole-transport layer. It is not known.

The present invention has a nip-type structure composed of a transparent electrode, an electron transport layer, a mesoporous _TiO2 layer, a perovskite layer using the mesoporous _TiO2 layer as a scaffold, a hole transport layer and a metal electrode, joined in this order. A solar cell is provided, wherein said hole-transporting layer comprises any of said hole-transporting materials according to the invention.

A perovskite crystal useful for obtaining a highly efficient photoelectric conversion element has a three-dimensional structure and has a composition formula: ABX ₃ (wherein A is a monovalent cation of an amine compound or an alkali metal element, and B is is a divalent cation of a metal element, and X is a monovalent anion of a halogen element).

In the composition formula, A is an organic ammonium such as methylammonium (CH ₃ NH ₃ ⁺ ) and formamidinium (HC(NH ₂ ) ₂ ⁺ ), or lithium (Li ⁺ ), sodium (Na ⁺ ), potassium ( K ⁺ ), rubidium (Rb ⁺ ) and at least one monovalent cation selected from alkali metal ions such as cesium (Cs ⁺ ), B is magnesium (Mg), tin (Sn) and lead (Pb) and X is at least one selected from chlorine (Cl), bromine (Br) and iodine (I).

Preferably, the perovskite is _MAPbI3 ( _lead methylammonium iodide), _{Cs0.05 ( FA0.85MA0.15} ) _0.95Pb ( _I0.89Br0.11 ) ₃ , or _FAPbI3 (lead formamidinium iodide).

If the hole-transporting material of the present invention is used, lithium bis(trifluoromethane)sulfonimide (LiTFSI), 4-tert-butyl pyridine (TBP), FK209 (tris( 2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tris[bis(trifluoromethane)sulfonimide]), F4TCNQ (tetrafluorotetracyanoquinodimethane), N(PhBr) Since there is no need to add dopants such _{as 3SbCl6} , it can exhibit stable solar cell characteristics.
Thus, in the perovskite solar cell of the invention, the hole-transporting layer consists solely of said hole-transporting material according to the invention.

The method for manufacturing a solar cell of the present invention comprises:
A step of forming an electron transport layer by forming a film of amorphous dense titanium oxide on the fluorine-doped tin oxide coat of the transparent electrode coated with fluorine-doped tin oxide;
forming a mesoporous titanium oxide layer on the electron transport layer;
forming a perovskite layer on the mesoporous titanium oxide layer by applying a perovskite solution;
Forming a hole-transporting layer on the perovskite layer by applying a solution of a hole-transporting material.

［式中、
Ｒ^１１は、水素原子、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、置換もしくは非置換のフェニル基、窒素含有ヘテロ芳香族基、もしくは、式（ＶＩ）：

（式中、
Ｒ^１３は、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_２～４アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_２～４アルコキシ基、アミノ基、もしくは置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_２～４アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_２～４アルコキシ基、もしくは置換もしくは非置換のフェニル基で置換されたアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基である。）で表されるアミド結合を有する有機基であって、かつ、
Ｒ^１２は、水素原子、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_２～４アルキル基、置換もしくは非置換のフェニル基、窒素含有ヘテロ芳香族基、もしくは、式（ＶＩ）で表されるアミド結合を有する有機基であり、
もし、前記直鎖状もしくは分岐鎖状Ｃ_２～４アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_２～４アルコキシ基、もしくは前記フェニル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基からなる群から選択され；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、置換もしくは非置換の５～８員のヘテロシクロアルキル基を形成し、ここに、前記ヘテロシクロアルキル基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記５～８員のヘテロシクロアルキル基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基からなる群から選択され、もしくは、いずれか２辺に置換もしくは非置換のベンゼン環が縮合していてもよく；または、
Ｒ^１１とＲ^１２は、それらが結合する窒素原子と一緒になって、単環若しくは縮合環からなる置換もしくは非置換のヘテロ芳香族環基を形成し、ここに、前記ヘテロ芳香族環基は、前記それらが結合する窒素原子以外に、酸素原子、窒素原子および硫黄原子からなる群から選択されるヘテロ原子を環内に含有してもよく、
もし、前記ヘテロ芳香族環が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基からなる群から選択される。］で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基であり、
Ｒ^１からＲ^１０のうち、上記式（Ｖ）で示されるアミノ基、N-置換アミノ基もしくはN,N-二置換アミノ基ではない置換基は、独立して、水素原子、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、置換もしくは非置換の直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、もしくは窒素含有芳香族環基であり、
もし、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルキル基、前記直鎖状もしくは分岐鎖状Ｃ_１～４アルコキシ基、もしくは前記窒素含有芳香族環基が置換されている場合は、その置換基は、F、Cl、BrおよびIから選択されるハロゲン原子、ヒドロキシル基、カルボニル基、ニトロ基、シアノ基、スルホニル基、トリフルオロメチル基からなる群から選択され、記号＊は結合点を意味する。｝で示されるN,N-ジ-置換フェニルアミノ基である。〕で示される正孔輸送材であって、
正孔輸送材料の溶液が、非ハロゲン溶媒中の前記正孔輸送材料溶液である。As one specific example, in the method for manufacturing a solar cell of the present invention, the hole-transporting material is an N,N-di-substituted phenylamino group represented by formula (IV),
{In the formula,
At least one of R ¹ through R ¹⁰ is independently of formula (V):

[In the formula,
R ¹¹ is a hydrogen atom, a substituted or unsubstituted linear or branched C _1-4 alkyl group, a substituted or unsubstituted phenyl group, a nitrogen-containing heteroaromatic group, or formula (VI):

(In the formula,
R ¹³ is a substituted or unsubstituted linear or branched C _2-4 alkyl group, a substituted or unsubstituted linear or branched C _2-4 alkoxy group, an amino group, or a substituted or unsubstituted A linear or branched C _2-4 alkyl group, a substituted or unsubstituted linear or branched C _2-4 alkoxy group, or an amino group substituted with a substituted or unsubstituted phenyl group, N -substituted amino group or N,N-disubstituted amino group. ) is an organic group having an amide bond represented by
R ¹² is a hydrogen atom, a substituted or unsubstituted linear or branched C _2-4 alkyl group, a substituted or unsubstituted phenyl group, a nitrogen-containing heteroaromatic group, or represented by formula (VI) is an organic group having an amide bond that
If the linear or branched C _2-4 alkyl group, the linear or branched C _2-4 alkoxy group, or the phenyl group is substituted, the substituent is F , Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group, a trifluoromethyl group; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a substituted or unsubstituted 5- to 8-membered heterocycloalkyl group, wherein said heterocycloalkyl group is said to be In addition to the bonding nitrogen atom, the ring may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom,
If said 5- to 8-membered heterocycloalkyl group is substituted, the substituent is a halogen atom selected from F, Cl, Br and I, hydroxyl group, carbonyl group, nitro group, cyano group , a sulfonyl group, and a trifluoromethyl group, or any two sides may be condensed with a substituted or unsubstituted benzene ring; or
R ¹¹ and R ¹² together with the nitrogen atom to which they are attached form a substituted or unsubstituted heteroaromatic ring group consisting of a single ring or a condensed ring, wherein the heteroaromatic ring group is , in addition to the nitrogen atom to which they are attached, may contain a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom and a sulfur atom in the ring,
If said heteroaromatic ring is substituted, the substituent may be a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group, a tri is selected from the group consisting of fluoromethyl groups; ], an N-substituted amino group or an N,N-disubstituted amino group,
Among R ¹ to R ¹⁰ , the substituents other than the amino group, N-substituted amino group or N,N-disubstituted amino group represented by the above formula (V) are independently a hydrogen atom, F, Cl, halogen atom selected from Br and I, hydroxyl group, carbonyl group, nitro group, cyano group, sulfonyl group, trifluoromethyl group, substituted or unsubstituted linear or branched C _1-4 alkyl group, substituted or an unsubstituted linear or branched C _1-4 alkoxy group, or a nitrogen-containing aromatic ring group,
If the linear or branched C _1-4 alkyl group, the linear or branched C _1-4 alkoxy group, or the nitrogen-containing aromatic ring group is substituted, the substitution The group is selected from the group consisting of a halogen atom selected from F, Cl, Br and I, a hydroxyl group, a carbonyl group, a nitro group, a cyano group, a sulfonyl group, a trifluoromethyl group, and the symbol * means the point of attachment. do. } is an N,N-di-substituted phenylamino group. ] A hole transport material represented by
A solution of a hole transport material is said hole transport material solution in a non-halogen solvent.

More specifically, as one specific example, in the above formula, R ¹¹ is methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group or a tert-butyl group, R ¹² is an ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group or tert-butyl group, and the non-halogen Solvents are alcohols selected from, but not limited to, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; diethyl ether, diisopropyl ether, Ethers selected from dibutyl ether, cyclopentyl methyl ether, etc.; cyclic ethers selected from tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, etc.; methyl acetate, ethyl acetate, butyl acetate, etc. Esters of the above alcohols with organic acids selected from acetic acid and the like; Ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone and the like; Aromatic hydrocarbons selected from toluene, xylene, mesitylene, anisole and the like selected from the group consisting of nitriles selected from acetonitrile and the like;

<Hole transport material 1>
Hole-transporting material 1 of the present invention is a conventional hole-transporting material spiro-OMeTAD, which was synthesized with reference to Patent Document 2.
¹ H NMR (300 MHz, CDCl3) δ 7.35 (d, J = 8.1 Hz, 4H), 6.92-6.88 (m, 16H), 6.80 (d, J = 2.2 Hz, 4H), 6.78-6.73 (m, 16H), 6.55 (d, J = 2.2 Hz, 4H), 3.77 (s, 24H)

<Hole transport material 2>
The hole transport material 2 of the present invention was synthesized according to Reaction Formula (1).

Compound 51 was synthesized with reference to Patent Document 3.
Compound 51 (2.3 g, 3.6 mmol, 1.0 equivalent), Compound 52 (Tokyo Chemical Industry, 4.6 g, 18.1 mmol, 5.0 equivalent), Palladium (II) acetate (Tokyo Chemical Industry, 0.03 g, 0.1 mmol, 0.04 equivalent), Tri-tert-butylphosphine (Fujifilm Wako Pure Chemical Industries, Ltd., 0.06 g, 0.3 mmol, 0.08 equivalent), sodium tert-butoxide (Tokyo Chemical Industry, 2.2 g, 22.9 mmol, 6.4 equivalent), and toluene 25 g were charged and heated to 100°C. The reaction was carried out by heating to . After completion of the reaction, the mixture was cooled to room temperature, 18 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 18 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole-transporting material 2 (1.2 g, yield 24%).
¹ H NMR (300 MHz, THF-d8) δ 7.28 (d, J = 8.4 Hz, 4H), 6.85 (d, J = 8.4 Hz, 16H), 6.67 (dd, J = 8.2, 1.3 Hz, 4H) , 6.60 (d, J = 8.4Hz, 16H), 6.52 (d, J = 1.8Hz, 4H), 2.86 (s, 48H)

<Hole transport material 3>
Hole-transporting material 3 (1.4 g; yield: 30%) was obtained in the same manner except that compound 53 was used in place of compound 52 in reaction formula (1). In addition, in the chemical structural formulas, sites represented only by bonds represent hydrocarbon groups (the same shall apply hereinafter).
¹ H NMR (300 MHz, DMSO-d6) δ 7.42 (d, J = 8.1 Hz, 4H), 6.83-6.78 (m, 24H), 6.66-6.61 (m, 12H), 6.18 (s, 4H), 3.70 (s, 12H), 2.85 (s, 24H)

<Hole transport material 4>
Hole-transporting material 4 (2.5 g; yield: 47%) was obtained in the same manner except that compound 54 was used in place of compound 52 in reaction formula (1).
¹ H NMR (300 MHz, CDCl3) δ 8.55 (d, J = 4.6, 1.6 Hz, 8H), 7.49 (d, J = 8.1 Hz, 4H), 7.40-7.37 (m, 16H), 7.03-6.93 ( m, 20H), 6.83 (d, J = 1.8Hz, 4H), 6.65 (d, J = 9.2Hz, 8H), 2.90 (s, 24H)

<Hole transport material 5>
Hole-transporting material 5 (0.2 g; yield 5%) was obtained in the same manner using compound 55 instead of compound 52 in reaction formula (1).
¹ H NMR (300 MHz, DMSO-d6) δ 7.39 (d, J = 8.1 Hz, 4H), 6.85-6.77 (m, 16H), 6.67-6.60 (m, 12H), 6.48 (d, J = 8.4 Hz, 8H), 6.15 (d, J = 1.8Hz, 4H), 5.01 (s, 8H), 3.70 (s, 12H)

<Hole transport material 6>
Hole-transporting material 6 (1.2 g; yield: 19%) was obtained in the same manner except that compound 56 was used in place of compound 52 in reaction formula (1).
¹ H NMR (300 MHz, CDCl3) δ 8.05 (d, J = 7.7 Hz, 8H), 7.57 (d, J = 8.1 Hz, 4H), 7.36-7.13 (m, 32H), 7.04-6.99 (m, 20H), 6.92 (d, J = 2.1Hz, 8H), 6.52 (d, J = 8.8Hz, 8H), 2.74 (s, 24H)

<Hole transport material 7>
Hole-transporting material 7 (0.8 g; yield 15%) was obtained in the same manner except that compound 57 was used in place of compound 52 in reaction formula (1).
¹ H NMR (300 MHz, CDCl3) δ 7.43 (d, J = 8.1 Hz, 4H), 7.01 (d, J = 8.8 Hz, 8H), 6.93-6.86 (m, 20H), 6.78 (d, J = 1.8Hz, 4H), 6.64 (d, J = 9.2Hz, 8H), 2.91 (s, 24H), 1.99 (s, 24H)

<Hole transport material 8>
A hole-transporting material 8 was obtained by the same procedure using compound 58 in place of compound 52 in reaction formula (1).

<Hole transport material 9>
A hole-transporting material 9 was obtained by the same procedure using compound 59 in place of compound 52 in reaction formula (1).

<Hole transport material 10>
The hole transport material 10 of the present invention was synthesized according to reaction formula (2).

Compound 60 was synthesized with reference to Patent Document 4.
Compound 51 (3.0 g, 4.7 mmol, 1.0 eq.), Compound 60 (5.8 g, 22.8 mmol, 4.8 eq.), Tris(dibenzylideneacetone)dipalladium(0) (Tokyo Chemical Industry, 0.2 g, 0.2 mmol, 0.04 eq.) ), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (Sigma-Aldrich, 0.4 g, 0.8 mmol, 0.16 equiv), sodium tert-butoxide (Tokyo Kasei Kogyo, 2.9 g, 30.4 mmol, 6.4 equivalents) and 80 g of xylene were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 80 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 80 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole transport material 10 (2.9 g, yield 45%).
¹ H NMR (300 MHz, CDCl3) δ 7.39 (d, J = 8.4 Hz, 4H), 7.02 (t, J = 8.1 Hz, 8H), 6.87 (dd, J = 8.2, 2.0 Hz, 4H), 6.77 ( d, J = 2.2Hz, 4H), 6.43 (t, J = 2.2Hz, 8H), 6.35-6.30 (m, 16H), 2.77 (s, 48H)

<Hole transport material 11>
The hole transport material 11 of the present invention was synthesized according to Reaction Formula (3) and Reaction Formula (4).

Compound 61 (Tokyo Chemical Industry, 13.3 g, 66.2 mmol, 1.0 equivalent), Compound 62 (Tokyo Chemical Industry, 8.8 g, 81.5 mmol, 1.2 equivalent), Tris(dibenzylideneacetone) dipalladium (0) (Tokyo Chemical Industry, 1.1 g, 1.2 mmol, 0.02 eq), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (Sigma-Aldrich, 2.2 g, 4.7 mmol, 0.07 eq), cesium carbonate (Tokyo Chemical Industry Co., Ltd., 57.6 g, 176.8 mmol, 2.7 equivalents) and 140 g of dimethoxyethane were charged and heated to 80°C to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, added with 200 g of water, and extracted with 200 g of ethyl acetate. The organic layer was washed twice with 200 g of water. The organic layer was concentrated under reduced pressure at 60° C. and purified by column chromatography to obtain compound 63 (14.7 g, yield 89%).
¹ H NMR (300 MHz, DMSO-d6) δ 7.71 (s, 1H), 7.09-6.93 (m, 5H), 6.73 (d, J = 8.4 Hz, 2H), 2.84 (s, 6H), 2.75 ( s, 6H)

Compound 51 (4.7 g, 7.4 mmol, 1.0 eq.), Compound 63 (10.0 g, 35.7 mmol, 4.8 eq.), Tris(dibenzylideneacetone) dipalladium (0) (Tokyo Chemical Industry Co., Ltd., 0.07 g, 0.07 mmol, 0.01 eq.) ), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (Sigma-Aldrich, 0.1 g, 0.3 mmol, 0.04 equiv), sodium tert-butoxide (Tokyo Kasei Kogyo, 4.3 g, 44.7 mmol, 6.0 equivalents) and 80 g of xylene were added, and the mixture was heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 80 g of water was added, and the precipitated solid was collected by filtration after stirring for 1 hour. Purification by column chromatography gave hole transport material 11 (9.7 g, yield 91%).
¹ H NMR (300 MHz, CDCl3) δ 7.39 (d, J = 8.1 Hz, 4H), 7.06-7.03 (m, 8H), 6.89 (d, J = 8.8 Hz, 8H), 6.81 (dd, J = 8.4, 1.8Hz, 4H), 6.72 (d, J = 8.4Hz, 4H), 6.63 (d, J = 8.8Hz, 8H), 6.52 (d, J = 1.8Hz, 4H), 2.92 (s, 48H)

<Hole transport material 12>
A hole-transporting material 12 (9.5 g; yield 84%) was obtained in the same manner except that compound 64 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.46 (d, J = 8.1 Hz, 4H), 7.10-7.06 (m, 16H), 6.84-6.79 (m, 12H), 6.44 (s, 4H), 2.99 ( s, 48H)

<Hole transport material 13>
A hole-transporting material 13 (8.6 g; yield 76%) was obtained in the same manner except that compound 65 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.42 (d, J = 8.1 Hz, 4H), 7.07-7.01 (m, 8H), 6.92 (d, J = 2.6 Hz, 4H), 6.88-6.75 (m, 16H), 6.41 (d, J=2.2Hz, 4H), 2.96 (s, 24H), 2.95 (s, 24H)

<Hole transport material 14>
Hole-transporting material 14 (4.6 g; yield: 41%) was obtained in the same manner using compound 66 instead of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.39 (d, J = 8.4 Hz, 4H), 6.96 (d, J = 8.8 Hz, 8H), 6.83 (dd, J = 9.0, 3.1 Hz, 8H), 6.77 -6.70 (m, 12H), 6.39 (d, J=1.8Hz, 4H), 2.92 (s, 48H)

<Hole transport material 15>
A hole-transporting material 15 (0.2 g; yield 6%) was obtained in the same manner except that compound 67 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.38 (d, J = 8.1 Hz, 4H), 6.98 (dd, J = 9.2, 3.7 Hz, 8H), 6.86-6.69 (m, 20H), 6.38 (d, J = 1.8Hz, 4H), 3.29 (q, J = 7.1Hz, 16H), 2.89 (s, 24H), 1.13 (t, J = 7.1Hz, 24H)

<Hole transport material 17>
A hole-transporting material 17 (1.8 g; yield 29%) was obtained in the same manner except that compound 68 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.36 (d, J = 8.1 Hz, 4H), 7.00 (d, J = 9.2, 8H), 6.79 (dd, J = 9.2, 3.3 Hz, 8H), 6.69 ( dd, J = 10.3, 2.6Hz, 12H), 6.36 (d, J = 2.2Hz, 4H), 3.29 (q, J = 7.0Hz, 32H), 1.12 (t, J = 7.0Hz 48H)

<Hole transport material 22>
A hole-transporting material 22 (1.1 g; yield 33%) was obtained in the same manner except that compound 69 was used in place of compound 63 in reaction formula (4).
^1H NMR (300 MHz, CDCl3) δ 7.41 (d, J = 8.1 Hz, 4H), 7.08-7.00 (m, 8H), 6.92
(d, J = 2.9Hz, 4H), 6.82-6.75 (m, 16H), 6.43 (d, J = 1.8Hz, 4H), 3.33 (q, J = 7.0Hz, 16H), 3.25 (q, J = 7.1Hz, 16H), 1.16 (t, J = 7.0Hz, 24H), 1.10 (t, J = 7.0Hz, 24H)

<Hole transport material 23>
A hole-transporting material 23 (4.7 g; yield 43%) was obtained in the same manner except that compound 70 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.40 (d, J = 8.1 Hz, 4H), 7.03 (dd, J = 9.2, 2.9 Hz, 4H), 6.97-6.91 (m, 8H), 6.79 (dd, J = 8.4, 2.2Hz, 4H), 6.70 (d, J = 9.2Hz, 4H), 6.48 (d, J = 2.2Hz, 4H), 6.43-6.35 (m, 8H), 2.94 (s, 24H), 2.89 (s, 24 hours)

<Hole transport material 24>
A hole-transporting material 24 (1.7 g; yield 15%) was obtained in the same manner except that compound 71 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.45 (d, J = 8.1 Hz, 4H), 7.15 (d, J = 2.6 Hz, 4H), 7.07 (dd, J = 9.2, 2.6 Hz, 4H), 6.81 -6.76 (m, 12H), 6.65-6.61 (m, 8H), 6.51 (d, J=1.8Hz, 4H), 2.98 (s, 24H), 2.80 (s, 24H)

<Hole transport material 25>
A hole-transporting material 25 (5.3 g; yield 43%) was obtained in the same manner except that compound 72 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.42 (d, J = 8.1 Hz, 4H), 7.19-7.12 (m, 8H), 7.02 (dd, J = 8.8, 2.6 Hz, 4H), 6.89-6.83 ( m, 12H), 6.75 (dd, J = 8.4, 2.2Hz, 4H), 6.62 (d, J = 1.5Hz, 4H), 2.67 (s, 48H), 2.19 (s, 12H)

<Hole transport material 26>
Hole-transporting material 26 (3.2 g; yield: 27%) was obtained in the same manner except that compound 73 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.41 (d, J = 8.1 Hz, 4H), 7.10-7.04 (m, 8H), 6.90 (d, J = 8.8 Hz, 8H), 6.84-6.72 (m, 16H), 6.51 (d, J = 1.8Hz, 4H), 3.85 (t, J = 4.6Hz, 16H), 3.11 (t, J = 4.6Hz, 16H), 2.95 (s, 24H)

<Hole transport material 29>
Hole-transporting material 29 (3.1 g; yield: 22%) was obtained in the same manner except that compound 74 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 7.48 (d, J = 8.4 Hz, 4H), 7.28-7.13 (m, 16H), 6.92 (dd, J = 8.1, 1.8 Hz, 4H), 6.84 (d, J = 8.8Hz, 16H), 6.64 (s, 8H), 6.57 (d, J = 1.8Hz, 4H), 1.50 (s, 72H)

<Hole transport material 30>
A hole-transporting material 30 (0.7 g; yield 7%) was obtained in the same manner except that compound 75 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, DMSO-d6) δ 9.86 (s, 8H), 7.53 (d, J = 8.1 Hz, 4H), 7.47 (d, J = 8.4 Hz, 16H), 6.84 (d, J = 8.4Hz, 16H), 6.75 (d, J = 9.5Hz, 4H), 6.29 (s, 4H), 2.01 (s, 24H)

<Hole transport material 31>
A hole-transporting material 31 (0.9 g; yield 6%) was obtained in the same manner except that compound 76 was used in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, DMSO-d6) δ 8.64 (s, 8H), 8.59 (s, 8H), 7.54 (d, J = 8.4 Hz, 4H), 7.45-7.37 (m, 32H), 7.25 ( t, J = 7.3Hz, 16H), 6.96-6.90 (m, 24H), 6.78 (d, J = 8.8Hz, 4H), 6.32 (s, 4H)

<Hole transport material 32>
The hole transport material 32 of the present invention was synthesized according to Reaction Formula (5) and Reaction Formula (6).

Compound 77 (Tokyo Chemical Industry, 15.0 g, 62.5 mmol, 1.0 equivalent), Compound 78 (Tokyo Chemical Industry, 13.4 g, 75.0 mmol, 1.2 equivalent), Tris(dibenzylideneacetone) dipalladium (0) (Tokyo Chemical Industry , 0.6 g, 0.6 mmol, 0.01 eq), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (Sigma-Aldrich, 1.2 g, 2.5 mmol, 0.04 eq), sodium tert-butoxide (Tokyo Kasei Kogyo Co., Ltd., 9.6 g, 99.9 mmol, 1.6 equivalents) and 400 g of xylene were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 400 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 200 g of water. The organic layer was concentrated under reduced pressure at 60° C. and purified by column chromatography to obtain compound 79 (15.0 g, yield 71%).
¹ H NMR (300 MHz, CDCl) δ 6.83-6.96 (m, 8H), 3.86 (t, J = 4.8 Hz, 4H), 3.06 (dd, J = 9.9, 5.5 Hz, 8H), 1.68-1.76 ( m, 4H), 1.51-1.58 (m, 2H)

Compound 51 (5.0 g, 7.9 mmol, 1.0 equiv.), Compound 79 (12.9 g, 38.0 mmol, 4.8 equiv.), Tris(dibenzylideneacetone)dipalladium(0) (Tokyo Chemical Industry Co., Ltd., 0.3 g, 0.3 mmol, 0.04 equiv.) ), 2-dicyclohexylphosphino-2′,4′,6-triisopropylbiphenyl (Sigma-Aldrich, 0.6 g, 1.3 mmol, 0.16 equiv), sodium tert-butoxide (Tokyo Chemical Industry, 4.9 g, 50.6 mmol, 6.4 equivalent), and 130 g of xylene were charged, and the reaction was carried out by heating to 100°C. After completion of the reaction, the mixture was cooled to room temperature, 130 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 70 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole-transporting material 32 (9.8 g, yield 75%).
¹ H NMR (300 MHz, CDCl3) δ 7.34 (d, J = 8.1 Hz, 4H), 6.73-6.94 (m, 36H), 6.61 (d, J = 1.8Hz, 4H), 3.84 (t, J = 4.6Hz, 16H), 3.05-3.08 (m, 32H), 1.67-1.74 (m, 16H), 1.51-1.58 (m, 8H)

<Hole transport material 33>
The hole transport material 33 of the present invention was synthesized according to reaction formula (7) and reaction formula (8).

Compound 80 (Tokyo Chemical Industry, 10 g, 41.3 mmol, 1.0 equivalent), Compound 81 (Tokyo Chemical Industry, 8.8 g, 49.5 mmol, 1.2 equivalent), Tris (dibenzylideneacetone) dipalladium (0) (Tokyo Chemical Industry, 0.4 g, 0.4 mmol, 0.01 eq), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (Sigma-Aldrich, 0.8 g, 1.6 mmol, 0.04 eq), sodium tert-butoxide (Tokyo Kasei Industrial, 6.5 g, 57.8 mmol, 1.6 equivalents) and 250 g of xylene were charged and heated to 110° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 100 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 100 g of water. The organic layer was concentrated under reduced pressure at 60° C. and purified by column chromatography to obtain compound 82 (7.6 g, yield 54%).
^1H NMR (300 MHz, DMSO-d6) δ 7.48 (s, 1H), 6.81-6.91 (m, 8H), 3.70-3.73 (m, 8H), 2.95-2.98 (m, 8H)

Compound 51 (2.7 g, 4.3 mmol, 1.0 eq.), Compound 82 (7.0 g, 20.5 mmol, 4.8 eq.), Tris(dibenzylideneacetone)dipalladium(0) (Tokyo Chemical Industry, 0.2 g, 0.2 mmol, 0.04 eq.) ), 2-dicyclohexylphosphino-2′,4′,6-triisopropylbiphenyl (Sigma-Aldrich, 0.3 g, 0.7 mmol, 0.16 equiv), sodium tert-butoxide (Tokyo Chemical Industry, 2.6 g, 27.3 mmol, 6.4 equivalent), and 130 g of xylene were charged, and the reaction was carried out by heating to 100°C. After completion of the reaction, the mixture was cooled to room temperature, 70 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 70 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole-transporting material 33 (1.9 g, yield 27%).
¹ H NMR (300 MHz, CDCl3) δ 7.34 (d, J = 8.1 Hz, 4H), 6.92 (d, J = 8.8 Hz, 16H), 6.74-6.80 (m, 20H), 6.60 (s, 4H) , 3.82-3.86 (m, 32H), 3.06-3.10 (m, 32H)

<Hole transport material 34>
A hole-transporting material 34 (1.5 g; yield 22%) was obtained in the same manner except that compound 83 was used in place of compound 82 in reaction formula (8).
¹ H NMR (300 MHz, CDCl3) δ 7.70 (s, 4H), 7.43 (d, J = 8.4 Hz, 4H), 7.31 (d, J = 8.8 Hz, 8H), 6.93-6.76 (m, 28H) , 6.63 (d, J = 1.8Hz, 4H), 3.84 (t, J = 4.8Hz, 16H), 3.09 (t, J = 4.6Hz, 16H), 2.16 (d, J = 9.5Hz, 12H)

<Hole transport material 35>
A hole-transporting material 35 (0.8 g; yield 12%) was obtained by the same procedure using compound 84 in place of compound 82 in reaction formula (8).
¹ H NMR (300 MHz, CDCl3) δ 7.36 (d, J = 8.1 Hz, 4H), 6.91-6.74 (m, 36H), 6.60 (s, 4H), 3.41 (t, J = 4.8Hz, 32H) , 2.76 (t, J=4.9Hz, 32H)

<Hole transport material 36>
A hole-transporting material 36 (2.9 g; yield 29%) was obtained in the same manner except that compound 85 was used in place of compound 82 in reaction formula (8).
^1H NMR (300 MHz, CDCl3) δ 7.51 (d, J = 8.1 Hz, 4H), 7.14 (t, J = 7.7 Hz, 32H), 7.04 (dd, J = 8.1, 1.8 Hz, 4H), 6.96 (d, J = 7.7Hz, 32H), 6.89 (t, J = 7.3Hz, 16H), 6.78 (s, 32H), 6.57 (d, J = 2.2Hz, 4H)

<Hole transport material 37>
A hole-transporting material 37 (3.4 g; yield 34%) was obtained in the same manner except that compound 86 was used in place of compound 82 in reaction formula (8).
¹ H NMR (300 MHz, THF-d8) δ 7.58 (d, J = 8.1 Hz, 4H), 7.12-6.75 (m, 88H), 6.71 (s, 16H), 6.60 (t, J = 2.0 Hz, 4H), 6.55 (d, J = 1.8Hz, 4H), 6.39 (ddd, J = 16.2, 8.0, 1.9Hz, 8H)

<Hole transport material 38>
A hole-transporting material 38 (1.2 g; yield 28%) was obtained by the same procedure using compound 87 in place of compound 63 in reaction formula (4).
¹ H NMR (300 MHz, CDCl3) δ 8.55 (dd, J = 4.6, 1.6 Hz, 8H), 7.48 (d, J = 8.1, 4H), 7.39-7.37 (m, 16H), 6.97-6.95 (m , 20H), 6.85-6.84 (m, 4H), 6.61-6.58 (m, 8H), 3.29 (q, J = 7.1Hz, 16H), 1.12 (t, J = 7.0Hz, 24H)

[Fabrication of solar cell]
Examples 1-40
A perovskite solar cell 1 having the structure shown in FIG. 1 was fabricated using a normal manufacturing process.
A glass plate 11 with an FTO transparent electrode 12 coated with fluorine-doped tin oxide (FTO) was prepared.

The FTO film was subjected to oxygen plasma treatment, and an electron transport layer 13 was formed by depositing amorphous dense TiO ₂ (compact TiO ₂ or c-TiO ₂ ) thereon by spray pyrolysis. Next, a mesoporous TiO ₂ (mp-TiO ₂ ) layer 14 was formed by spin-coating a titanium oxide nanoparticle colloid (at 2,000 rpm for 30 seconds) followed by heating at 450° C. for 30 minutes.

Using this mp-TiO ₂ layer as a scaffold, a perovskite layer is formed.
First, lead iodide (PbI ₂ ) and methylammonium iodide (CH ₃ NH ₃ I) were mixed at a molar ratio of 1.575:1.5, and added to a mixed solvent of DMF and DMSO (volume ratio 3:1). Dissolved to prepare a solution of perovskite _MAPbI3 .
A perovskite layer 15 was formed on the mp-TiO ₂ layer by spin coating. After dropping the solution, rest for 15 seconds, accelerate to 5,000 rpm over 2 seconds, hold at 5,000 rpm for 5 seconds, and rest for 1 second. Further, 200 μL of additional chlorobenzene was added dropwise 20 seconds after the start.
The resulting laminate was then thermally annealed with a temperature profile of 40° C. for 5 minutes, 60° C. for 5 minutes, 70° C. for 5 minutes, 100° C. for 10 minutes, and 120° C. for 10 minutes. did

Next, 0.69 molar equivalents of LiFTSI and 2.96 molar equivalents of TBP as dopants were dissolved in an organic solvent to prepare an HTM solution. In the case of dopant-free, a dopant-free HTM solution was prepared by dissolving only each hole-transporting material in an organic solvent.
When hole transport materials 1, 2, 3 were used, 71 mM solutions in chlorobenzene were prepared. When hole transport materials 10, 31, 35 were used, 18 mM solutions in chlorobenzene were prepared. When hole transport material 29 was used, a 9 mM solution in chlorobenzene was prepared. When hole transport material 5 was used, a 36 mM solution was prepared in a 1/1 volume ratio chlorobenzene/chloroform mixed solvent. When hole-transporting materials 11, 12, 14, 23, 24, 25, 26, 32 were used, 9 mM solutions were prepared in a 1/1 volume ratio chlorobenzene/chloroform mixed solvent. When hole-transporting materials 4, 13, and 19 were used, 4.5 mM solutions were prepared in a 1/1 volume ratio chlorobenzene/chloroform mixed solvent. When hole transport material 17 was used, a 6 mM solution was prepared in a 1/1 volume ratio chlorobenzene/chloroform mixed solvent.

Hole transport material 1 is the conventional hole transport material spiro-OMeTAD and a control compound. In the basic skeleton represented by formula (III), the type and substitution of substituents on the phenyl ring of R ⁰ (substituted diphenylamino group represented by formula (IV)) (hereinafter referred to as "substituents on the phenyl ring") By changing the position, hole-transporting materials 2 to 40 exhibiting excellent photoelectric conversion efficiency even without dopants were investigated.
An HTM solution or a dopant-free HTM solution was dropped onto the perovskite layer 15, and a hole transport layer 16 was formed by spin coating (3,000 rpm for 30 seconds).

Finally, a metal electrode 17 was formed by vapor-depositing Au to a thickness of 100 nm on the surface of the hole transport layer 16 .

Terminals were provided so that the transparent FTO electrode 12 was the negative electrode (anode) and the metal electrode was the positive electrode (cathode), and the perovskite solar cell 1 was constructed.

[Evaluation of solar cell characteristics]
Tables 1 to 5 show the results of measuring the highest occupied molecular orbital level (E _HOMO ) measured in solution and the photoelectric conversion efficiency (PCE) of the solar cell for each hole transport material 1 to 40 (in the table, ( ) Numerical values shown within are estimated values, and the symbol --- means unmeasured. PCE in the presence of dopant is indicated by PCE _PR , PCE in the absence of dopant is indicated by PCE _AB , and the ratio of PCE _AB to PCE _PR is indicated as variation. If the variation is less than 1, the HTM of interest represents poor performance in the absence of the dopant. Therefore, the variation should preferably be close to 1, and more preferably greater than 1.

(1) Approach by changing the electron-withdrawing properties of substituents on the phenyl ring The substituents on the two phenyl rings in the hole-transporting material 1 are p-position methoxy groups (-OMe: Me represents a methyl group). , these were changed to dimethylamino groups (-NMe ₂ ) for a compound (hole-transporting material 2).
It was shown that the highest occupied molecular orbital level (E _HOMO ) can be greatly tuned by changing the substituents on the two phenyl rings from —OMe to —NMe ₂ .
Also, hole transport material 2 exhibited a lower PCE than hole transport material 1 in the presence of dopants (LiTFSI and TBP), whereas hole transport material 1 and hole transport material 1 2's PCE became comparable. A higher change in PCE (PCE _AB /PCE _PR ) by omitting the dopant was obtained for hole transport material 2 than for hole transport material 1 .

The substituents on the two phenyl rings in the hole transport material 1 are p-position methoxy groups (-OMe: Me represents a methyl group), but the substituent on one phenyl ring is a dimethylamino group (- NMe ₂ ) and another substituent on the phenyl ring was changed to a methoxy group (--OMe) or a 4-pyridinyl group (--C ₅ H ₄ N) (hole-transporting materials 3 or 4). , and the substituent on one phenyl ring to —NH ₂ and the substituent on the other phenyl ring to —OMe (hole transport material 5).
By varying the substituents on one phenyl ring while changing the substituents on one phenyl ring from —OMe to —NMe ₂ , the highest occupied molecular orbital level (E _HOMO ), PCE, and It was shown that PCE variation (PCE _AB /PCE _PR ) can be adjusted by excluding dopants.

(2) Approach by changing the substitution position of the substituent on the phenyl ring In the hole transport material 2, there are substituents at the p-position on the two phenyl rings, but the substitution position on the two phenyl rings is changed to the m-position. The hole transport material 10 was confirmed.
It was shown that by changing the substitution positions on the phenyl ring, the highest occupied molecular orbital level (E _HOMO ), PCE, and variation of PCE by excluding the dopant (PCE _AB /PCE _PR ) can be adjusted.

(3) Approach of introducing an N,N-disubstituted amino group at the p-position and further introducing a different substituent In hole-transporting material 2, only dimethylamino groups are bound to the p-positions of the two phenyl rings. However, hole transport materials 11 to 28 having various substituents (cyano group, fluorine atom, trifluoromethyl group, methyl group) introduced on one or two phenyl rings were confirmed. In addition, a hole transport material 26 in which —CN was introduced onto one phenyl ring and a morpholino group was introduced to the p-position of the other phenyl ring was confirmed.
Eliminate the highest occupied molecular orbital level (E _HOMO ), PCE, and dopants by introducing different substituents on the two phenyl rings other than N,N-disubstituted amino groups at the p-position It was shown that the PCE variation (PCE _AB /PCE _PR ) can be adjusted by

(4) Approach by structural change of N,N-disubstituted amino group Hole transport materials 29 to 40 with various substituents (tert-butoxycarbonylamino group, acetylamino group, phenylureido group, piperidino group, morpholino group, thiomorpholino group, diphenylamino group) bonded to the phenyl ring confirmed.
By excluding the highest occupied molecular orbital level (E _HOMO ), PCE, and dopants by introducing various substituents attached to the phenyl rings through the nitrogen atom as substituents on the two phenyl rings. It was shown that the variation of PCE (PCE _AB /PCE _PR ) can be adjusted.

(5) Effect on Various Perovskite Using various perovskites and hole-transporting materials 14, perovskite layers and hole-transporting layers were formed under the following conditions. A dopant-free solar cell was produced under the same conditions as in Example 14 except for the above.
(a) Perovskite layer formation of _Cs0.05 ( _FA0.85MA0.15 ) _{0.95Pb ( I0.89Br0.11} ) ₃ First, formamidinium iodide (FAI), lead iodide ( _PbI2 ), methylammonium _bromide ( _CH3 NH ₃ Br) and lead bromide (PbBr ₂ ) were mixed at a molar ratio of 1:1.16:0.18:0.14, dissolved in a mixed solvent of DMF and DMSO (volume ratio of 4:1), and iodine was added. A solution of perovskite Cs _0.05 (FA _0.85 MA _0.15 ) _0.95 Pb(I _0.89 Br _0.11 ) ₃ was prepared by adding a cesium chloride (CsI) 1.5 M DMSO solution to a molar ratio of 0.06.
A perovskite layer 15 was formed on the mp-TiO ₂ layer by spin coating. After dropping the solution, rest for 30 seconds, accelerate to 1,000 rpm over 1 second, hold at 1,000 rpm for 10 seconds, accelerate to 6,000 rpm over 1 second, hold at 6,000 rpm for 20 seconds, hold for 5 seconds. was stopped by . Further, 200 μL of additional chlorobenzene was added dropwise 59 seconds after the start.
After that, the obtained laminate was subjected to a thermal annealing treatment with a temperature profile of 40° C. for 5 minutes, 60° C. for 5 minutes, 70° C. for 5 minutes, and 100° C. for 60 minutes.
(b) Perovskite layer formation of FAPbI ₃ First, formamidinium lead iodide (FAPbI ₃ ) and methylammonium iodide (MACl) were mixed at a molar ratio of 1:0.35, and a mixed solvent of DMF and DMSO (volume ratio 4:1) to prepare a solution of perovskite _FAPbI3 .
A perovskite layer 15 was formed on the mp-TiO ₂ layer by spin coating. After dropping the solution, rest for 20 seconds, accelerate to 6,000 rpm over 1 second, maintain at 6,000 rpm for 50 seconds, and rest for 1 second. Further, 200 μL of additional chlorobenzene was added dropwise 31 seconds after the start.
After that, the obtained laminate was subjected to a thermal annealing treatment at 150° C. for 10 minutes.
(c) Formation of Dopant-Free Hole-Transporting Layer Next, only the hole-transporting material 14 was dissolved in a mixed solvent of chlorobenzene/chloroform (1/1 by volume) to prepare a 3 mM solution.
Table 6 shows the results of measuring the photoelectric conversion efficiency (PCE) of the obtained solar cell.

It was confirmed that the hole-transporting material of the present invention is dopant-free and exhibits high photoelectric conversion efficiency for any perovskite.

(6) Comparison of Change in Conversion Efficiency Over Time with and without Dopant Solar cells fabricated using hole transport material 1 (spiro-OMeTAD) and hole transport material 14 with or without addition of LiTFSI and TBP as dopants. For (Examples 1 and 14), an 85° C. thermal stability test was conducted to measure changes in conversion efficiency over time. The 85°C thermal stability test was conducted using an ETTAS constant temperature dryer (AS ONE OF-300) at a setting of 85°C (the cell was not sealed).
For the hole transport material 1, it was found that the conversion efficiency of the system to which the dopant was added decreased sharply immediately after the start of the test, and the conversion efficiency of the system to which no dopant was added was stable, but the initial conversion efficiency decreased ( Figure 2a). On the other hand, in the hole transport material 14, the conversion efficiency decreased in the system to which the dopant was added, and was stable in the system to which the dopant was not added. It was also confirmed that the dopant addition did not reduce the initial conversion efficiency (Fig. 2b).

(7) Effect of Solvent Used in Forming Hole Transport Layer From the viewpoint of reducing environmental load, it is required not to use a halogen-based solvent in the manufacturing process of a solar cell.
Therefore, by comparing the hole transport materials 14 and 17, which were confirmed to have excellent solar cell characteristics, a chain of alkyl groups bonded to the N,N-disubstituted amino group represented by the formula (V) The effect of length on solubility in various solvents was investigated.
Specifically, 1 g of each hole transport material was added to 10 ml of solvent in a beaker, stirred with a magnetic stirrer at room temperature (about 25 ° C.), and the difficulty of dissolution was evaluated according to the following criteria. The results are shown in Table 7.
○: Easily soluble (completely dissolved)
×: Insoluble (Part or all remained.)

It was confirmed that the hole-transporting material 17) represented by the formula (V) in which the N,N-disubstituted amino group is an N,N-diethylamino group exhibits high solubility even in non-halogen solvents. Therefore, when the hole transport material 17 was used to form the hole transport layer, a 4 mM solution in ethyl acetate was prepared instead of the halogen-based solvent. Otherwise, a solar cell was formed under the same conditions as in Example 17.
Table 8 shows the results of measuring the photoelectric conversion efficiency (PCE) of the obtained solar cell.

The hole-transporting layer formed using a hole-transporting material solution prepared in a non-halogen solvent (ethyl acetate) was compared to the hole-transporting layer formed using a conventional halogen solvent (chlorobenzene/chloroform mixed solvent). also showed similar photovoltaic efficiency (PCE) without any manufacturing issues.

(8) Summary From the above multiple approaches, any perovskite can be selected as a hole-transporting material as long as it is a compound in which a substituted diphenylamino group represented by formula (IV) is bonded to the basic structure represented by formula (III). It was found that a stable photoelectric conversion efficiency was exhibited even in the absence of a dopant.
In particular, one or two substituents on the phenyl ring of said substituted diphenylamino group are substituents bonded to the phenyl ring through a nitrogen atom (amino group of formula (V), N-substituted amino group or N,N-disubstituted amino group), more preferably N,N-disubstituted amino group. In particular, it is particularly preferred that the substituents on the two phenyl rings of said substituted diphenylamino group are substituted at the p-position with N,N-disubstituted amino groups.
In addition, if one substituent in the N,N-disubstituted amino group on one or two phenyl rings of the substituted diphenylamino group is a linear or branched C _2-4 alkyl group, It has been found that halogen solvents can be used to prepare hole transport material solutions.

で示される、スピロビフロオレン化合物の2,2’,7,7’-テトラキス(N,N-ジ-p-フェニルアミン)-9,9’-スピロビフルオレン（化合物１００、「オクタブロモ置換体」）を合成した。[Precursor of hole transport material]
The present inventors next investigated spiro-OMeTAD and its superior properties in a nip-type (forward-type) solar cell (Fig. 1) that employs mp- _TiO2 as a scaffold to form perovskite crystals. We have developed useful precursors for highly efficient synthesis of hole-transporting materials.
In the present invention, as an example of useful precursor of hole transport material (HTM) containing N,N-di-p-substituted phenylamino group, formula (XIa):

2,2',7,7'-Tetrakis(N,N-di-p-phenylamine)-9,9'-spirobifluorene (Compound 100, "octabromo-substituted ”) was synthesized.

As the octabromo-substituted product of the present invention, compound 100 was synthesized according to Reaction Formula (9) and Reaction Formula (10).

First, referring to Non-Patent Document 3, 2,2',7,7'-tetrabromo-9,9'-spirobifluorene (compound 101) was synthesized and purified by recrystallization with dioxane. Next, with reference to Patent Document 2, compound 101 (20.0 g, 31.6 mmol, 1.0 equivalent), compound 102 (Tokyo Chemical Industry, 25.7 g, 151.9 mmol, 4.8 equivalent), palladium acetate (II) (Tokyo Chemical Industry , 0.3 g, 1.3 mmol, 0.04 equivalents), tri-tert-butylphosphine (Fujifilm Wako Pure Chemical Industries, Ltd., 0.5 g, 2.5 mmol, 0.08 equivalents), sodium tert-butoxide (Tokyo Chemical Industry, 19.5 g, 202.5 mmol, 6.4 equivalent), and 500 g of xylene were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 250 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 250 g of water. The organic layer was concentrated under reduced pressure at 60° C. and purified by column chromatography to obtain compound 103 (24.0 g, yield 77.0%).
¹ H NMR (300 MHz, CDCl3) δ 7.45 (d, J = 8.4 Hz, 4H), 7.19 (t, J = 7.9 Hz, 16H), 7.00-6.91 (m, 28H), 6.69 (d, J = 1.5Hz, 4H)

Compound 103 (24.0 g, 24.4 mmol, 1.0 equivalent), N-bromosuccinimide (Tokyo Kasei Kogyo, 34.7 g, 195 mmol, 8.0 equivalent), and 350 g of chloroform were charged, and the reaction was carried out at room temperature. After completion of the reaction, 350 g of water was added, and after stirring for 1 hour, the aqueous layer was removed. The organic layer was washed twice with 350 g of water. The organic layer was concentrated under reduced pressure at 60° C. and purified by column chromatography to obtain compound 100 (38.9 g, yield 98.8%).
¹ H NMR (300 MHz, CDCl) δ 7.54 (d, J = 8.1 Hz, 4H), 7.31 (dt, J = 9.5, 2.6 Hz, 16H), 6.96 (dd, J = 8.2, 2.0 Hz, 4H), 6.81 (dt, J = 9.5, 2.6 Hz, 16H), 6.57 (d, J = 1.8 Hz, 4H)

[Hole transport material]
The octabromo-substituted compound (compound 100) of the present invention is used for hole transport that can exhibit high photoelectric conversion efficiency even when used in a dopant-free hole transport layer in a nip-type (forward type) solar cell. synthesized the material.

<Hole transport material 1>
Hole transport material 1 of the present invention was synthesized according to reaction formula (11).

Compound 100 (5.0 g, 3.0 mmol, 1.0 equiv.), tris(dibenzylideneacetone)dipalladium(0) (Tokyo Kasei Kogyo, 0.6 g, 0.3 mmol, 0.10 equiv.), 2-dicyclohexylphosphino-2',4',6'-Triisopropylbiphenyl (Sigma-Aldrich, 0.3 g, 0.6 mmol, 0.2 eq), sodium tert-butoxide (Tokyo Chemical Industry, 5.35 g, 55.7 mmol, 18 eq), methanol (Fujifilm Wako Pure Chemical, 9.6 g, 300 mmol, 100 equivalents) and 50 g of xylene were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 100 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 100 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole transport material 1 (1.2 g, yield 32%).
¹ H NMR (300 MHz, CDCl3) δ 7.35 (d, J = 8.1 Hz, 4H), 6.92-6.88 (m, 16H), 6.80 (d, J = 2.2 Hz, 4H), 6.78-6.73 (m, 16H), 6.55 (d, J = 2.2 Hz, 4H), 3.77 (s, 24H)

<Hole transport material 29>
Hole-transporting material 29 was synthesized according to reaction formula (12) using compound 100, which is an octabromo-substituted compound of the present invention, as a starting material.

Compound 100 (5.0 g, 3.0 mmol, 1.0 equivalent), tert-butyl carbamate (Tokyo Chemical Industry, 3.6 g, 30.9 mmol, 10.0 equivalent), tris(dibenzylideneacetone) dipalladium(0) (Tokyo Chemical Industry, 0.6 g, 0.3 mmol, 0.10 equiv), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (Sigma-Aldrich, 0.3 g, 0.6 mmol, 0.2 equiv), cesium carbonate (Tokyo Chemical Industry, 18.1 g, 55.7 mmol, 18 equivalents), 50 g of xylene, and 50 g of tert-butyl alcohol were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 200 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 200 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole-transporting material 29 (3.2 g, yield 54.4%).
¹ H NMR (300 MHz, CDCl3) δ 7.48 (d, J = 8.4 Hz, 4H), 7.28-7.13 (m, 16H), 6.92 (dd, J = 8.1, 1.8 Hz, 4H), 6.84 (d, J = 8.8Hz, 16H), 6.64 (s, 8H), 6.57 (d, J = 1.8Hz, 4H), 1.50 (s, 72H)

<Hole transport material 35>
The hole transport material 35 was synthesized according to reaction formula (13).

Compound 100 (5.0 g, 3.0 mmol, 1.0 equivalent), thiomorpholine (Tokyo Chemical Industry, 3.2 g, 30.9 mmol, 10.0 equivalent), tris(dibenzylideneacetone) dipalladium (0) (Tokyo Chemical Industry, 0.6 g, 0.3 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (Sigma-Aldrich, 0.3 g, 0.6 mmol, 0.2 eq), cesium carbonate (Tokyo Chemical Industry, 18.1 g, 55.7 eq) mmol, 18 equivalents) and 100 g of xylene were charged and heated to 100° C. to carry out the reaction. After completion of the reaction, the mixture was cooled to room temperature, 200 g of water was added, and the aqueous layer was removed after stirring for 1 hour. The organic layer was washed twice with 200 g of water. After the organic layer was concentrated under reduced pressure at 60° C., it was purified by column chromatography to obtain hole-transporting material 35 (1.0 g; yield 17%).
¹ H NMR (300 MHz, CDCl3) δ 7.36 (d, J = 8.1 Hz, 4H), 6.91-6.74 (m, 36H), 6.60 (s, 4H), 3.41 (t, J = 4.8Hz, 32H) , 2.76 (t, J=4.9Hz, 32H)

[Fabrication of solar cell]
A perovskite solar cell 1 having the structure shown in FIG. 1 was fabricated using a normal manufacturing process.
A glass plate 11 with an FTO transparent electrode 12 coated with fluorine-doped tin oxide (FTO) was prepared.

The FTO film was subjected to an oxygen plasma treatment, and an electron transport layer 13 was formed by forming an amorphous compact TiO ₂ (compact TiO ₂ ; c-TiO ₂ ) thereon by a spray pyrolysis method. Next, a mesoporous TiO ₂ (mp-TiO ₂ ) layer 14 was formed by spin-coating a titanium oxide nanoparticle colloid (at 2,000 rpm for 30 seconds) followed by heating at 450° C. for 30 minutes.

Using this mp-TiO ₂ layer as a scaffold, a perovskite layer is formed.
First, lead iodide (PbI ₂ ) and methylammonium iodide (CH ₃ NH ₃ I) were mixed at a molar ratio of 1.575:1.5, and added to a mixed solvent of DMF and DMSO (volume ratio 3:1). dissolved to prepare a perovskite solution.
A perovskite layer 15 was formed on the mp-TiO ₂ layer by spin coating. After dropping the solution, rest for 15 seconds, accelerate to 5000 rpm over 2 seconds, hold at 5000 rpm for 5 seconds, and rest for 1 second. Further, 200 μL of additional chlorobenzene was added dropwise 20 seconds after the start.
After that, the resulting laminate is thermally annealed with a temperature profile of 40° C. for 5 minutes, 60° C. for 5 minutes, 70° C. for 5 minutes, 100° C. for 10 minutes, and 120° C. for 10 minutes. did

Next, hole transport material 29, 0.69 molar equivalents of LiFTSI and 2.96 molar equivalents of TBP as dopants were dissolved in an organic solvent to prepare an HTM solution. In the case of dopant-free, a dopant-free HTM solution was prepared by dissolving only each hole-transporting material in an organic solvent.
When hole transport material 29 was used, a 4.5 mM solution was prepared in a 1/1 volume ratio chlorobenzene/chloroform mixed solvent. When hole transport material 1 was used, a 71 mM solution in chlorobenzene was prepared.

Using the hole transport material 1, 29 or 35, the HTM solution or the dopant-free HTM solution was dropped on the perovskite layer 15, and the hole transport layer 16 was formed by spin coating (3,000 rpm for 30 seconds).

Finally, a metal electrode 17 was formed by vapor-depositing Au to a thickness of 100 nm on the surface of the hole transport layer 16 .

Terminals were provided so that the transparent FTO electrode 12 was the negative electrode (anode) and the metal electrode was the positive electrode (cathode), and the perovskite solar cell 1 was constructed.

[Evaluation of solar cell characteristics]
Table 9 shows the highest occupied molecular orbital level (E _HOMO ) of each hole transport material and the photoelectric conversion efficiency (PCE) of a solar cell using them. PCE in the presence of dopant is indicated by PCE _PR , PCE in the absence of dopant is indicated by PCE _AB , and the ratio of PCE _AB to PCE _PR is indicated as variation. If the variation is less than 1, the HTM of interest represents poor performance in the absence of the dopant. Therefore, the variation should preferably be close to 1, and more preferably greater than 1.

<Measurement method>
(1) Highest occupied orbital level (E _HOMO )
Each hole transport material was dissolved in 0.1M tetraethylammonium perchlorate (TEAP) supporting electrolyte solution (methylene chloride), and DPV (differential pulse voltammetry) was measured using an electrochemical analyzer (ALS/CH Instruments 610B). , the highest occupied orbital level (E _HOMO ) was calculated with ferrocene as a reference substance of -4.80 eV. Hole transport materials 30, 31, and 32 were measured by replacing the solvent of the 0.1M tetraethylammonium perchlorate (TEAP) supporting electrolyte solution with DMF.

(2) Solar cell photoelectric conversion efficiency (PCE)
Using a solar simulator (XIL-05B100KP, manufactured by SELIC Co., Ltd.), AM1.5G, 100mW/cm ² simulated sunlight was applied to the solar cell to evaluate IV characteristics.

A perovskite solar cell using the hole-transporting material of the present invention exhibits high photoelectric conversion efficiency without adding dopants such as LiTFSI and TBP to the hole-transporting layer, and provides a solar cell with stable photoelectric characteristics. be able to.
The hole-transporting material of the present invention facilitates adjustment of the highest occupied molecular orbital level (E _HOMO ) and can be applied to various perovskites.
In addition, a tandem solar cell can be configured in which perovskite uses light on the short wavelength side and silicon uses light on the long wavelength side, and higher photoelectric conversion efficiency can be achieved.
Such solar cells are used in roof-mounted panels (houses, buildings, factories), roof-mounted (houses, buildings, factories, garages, greenhouses), wall-mounted (houses, buildings, factories), window glass, blinds, It can be used in various fields such as light shielding sheets, solar power plants, IoT terminal power supplies (RFID tags, sensors, small electronic devices), mobile solar chargers, artificial satellites, automobiles, drones, and solar planes.

1 perovskite solar cell 11 glass substrate 12 transparent electrode 13 electron transport layer 14 mesoporous metal oxide 15 perovskite layer 16 hole transport layer 17 metal electrode

Claims (9)

Formula (III):

[In the formula,
The four R ^0s are identical and have the formula:

N,N-di-substituted phenylamino groups selected from the group consisting of ] , a hole-transporting material. In formula (III), the four R ⁰ are the same and have the following formula:

2. The hole transport material of claim 1 , which is an N,N-di-(p-substituted phenyl)amino group selected from the group consisting of: A solar cell with a nip-type structure composed of a transparent electrode, an electron-transporting layer, a mesoporous _TiO2 layer, a perovskite layer using the mesoporous _TiO2 layer as a scaffold, a hole-transporting layer, and a metal electrode, joined in this order. 3. A perovskite solar cell, wherein said hole-transporting layer comprises the hole-transporting material according to claim 1 or 2 . The perovskite is represented by the compositional formula: ABX ₃ , where A is an organic ammonium such as methylammonium (CH ₃ NH ₃ ⁺ ) and formamidinium (HC(NH ₂ ) ₂ ⁺ ), or lithium (Li ⁺ ), At least one monovalent cation selected from alkali metal ions consisting of sodium (Na ⁺ ), potassium (K ⁺ ), rubidium (Rb ⁺ ) and cesium (Cs ⁺ ), and B is magnesium (Mg) and tin is a divalent cation of at least one metal element selected from (Sn) and lead (Pb), and X is at least one selected from chlorine (Cl), bromine (Br) and iodine (I); 4. The perovskite solar cell of claim 3 . 5. _The method of claim 4 , wherein the perovskite is _MAPbI3 (lead methylammonium iodide), _Cs0.05 ( _FA0.85MA0.15 ) _0.95Pb ( _I0.89Br0.11 ) _{3 ,} or _FAPbI3 (lead formamidinium iodide). perovskite solar cell. 4. The perovskite solar cell of claim 3 , wherein the hole-transporting layer consists solely of said hole-transporting material. A method for manufacturing a perovskite solar cell according to claim 3 ,
A step of forming an electron transport layer by forming a film of amorphous dense titanium oxide on the fluorine-doped tin oxide coat of the fluorine-doped tin oxide-coated transparent electrode;
forming a mesoporous titanium oxide layer on the electron transport layer;
forming a perovskite layer on the mesoporous titanium oxide layer by applying a perovskite solution;
A method of manufacturing comprising forming a hole-transporting layer on said perovskite layer by applying a solution of a hole-transporting material. 8. The manufacturing method according to claim 7 , wherein the solution of hole transport material is a solution of said hole transport material in a non-halogen solvent. The non-halogen solvent is alcohol selected from n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; diethyl ether, diisopropyl ether, dibutyl ether , cyclopentyl methyl ether; cyclic ethers selected from tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran; methyl acetate, ethyl acetate, butyl acetate, the alcohol and , esters with organic acids selected from acetic acid; ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.; aromatic hydrocarbons selected from toluene, xylene, mesitylene, anisole; The production method according to claim 8 , wherein the nitriles are selected from

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