WO2018165101A1

WO2018165101A1 - Dispiro-oxepine derivatives for optoelectronic semiconductors

Info

Publication number: WO2018165101A1
Application number: PCT/US2018/021058
Authority: WO
Inventors: Muhammad Sohail
Original assignee: Qatar Foundation For Education, Science And Community Development
Priority date: 2017-03-06
Filing date: 2018-03-06
Publication date: 2018-09-13

Abstract

The dispiro-oxepine derivative for optoelectronic semiconductors includes compounds having the formula (I): where R is hydrogen, C1-C18 alkyl, C1-C18 perfluoroalkyl, or (CH2) n -(CF2) n -F where n=1-18; and where Ar is p-MeOC6H4, p-MeSC6H4, phenyl, p-C6H13OC6H4, p-C6H13SC6H4, p-MeC6H4, or p-PhC6H4. Compounds of the above formula serve as efficient hole transporting materials when applied as a coating on an electron transporting material infiltrated with a perovskite absorbing material to form semiconductors for perovskite solar cells and other optoelectronic devices.

Description

DISPIRO-OXEPINE DERIVATIVES FOR

OPTOELECTRONIC SEMICONDUCTORS

TECHNICAL FIELD

The disclosure of the present patent application relates to optoelectronic semiconductors, and particularly to dispiro-oxepine derivatives for optoelectronic semiconductors that serve as an efficient hole transporting material when applied as a coating on an electron transporting material infiltrated with a perovskite absorbing material to form semiconductors for perovskite solar cells and other optoelectronic devices.

BACKGROUND ART The conversion of solar energy to electrical current using thin film third generation photovoltaics (PV) has been widely explored for the last two decades. The sandwich/monolithic-type PV devices, consisting of a mesoporous photoanode with an organic/inorganic light harvester, redox electrolyte/solid- state hole conductor, and counter electrode, have attracted significant interest due to the ease of their fabrication, their flexibility in the selection of materials, and their low cost effective production.

In recent years, perovskite-based solar cells (PSCs) have become particularly appealing in the photovoltaics field, since they have inexpensive precursors, simple fabrication methods, and remarkably high power conversion efficiency (PCE) values. A typical PSC configuration is composed of an electron transporting material (ETM), which is infiltrated with the perovskite absorbing material and coated with a hole transporting material (HTM), which plays an important role to facilitate the movement of holes from perovskite to the counter electrode.

Perovskite-based and other types of solid state solar cells generally contain an organic HTM layer for transporting holes created by charge separation at the light harvester to the counter electrode and/or cathode for filling up with incoming electrons, thereby closing the electric circuit and rendering the devices regenerative.

Spiro-based organic semiconductors have attracted considerable attention, more precisely, 2,2' ,7,7'-tetrakis-(N,N-di-4-methoxyphenylamine)-9,9'-spirobifluorene (spiro- OMeTAD) has been selected as the benchmark HTM for PSC. Currently, most performing solid-state devices use doped spiro-OMeTAD as a HTM. The relatively low PCE of solid- state devices was often ascribed to the low hole mobility in spiro-OMeTAD, which causes interfacial recombination losses by two orders of magnitude higher than in electrolyte-based, dye-sensitized solar cells (DSCCs).

Further, the use of spiro-OMeTAD as a hole transporting material may trigger instability in such solid-state solar cells. Because spiro-OMeTAD has two oxidation potentials that are close, this HTM in the oxidized form is able to form a di-cation, which, in turn, can dismutate and might cause device instability. Further, since spiro-OMeTAD is present in a semi-crystalline form, there is the risk that it will (re)crystallize in the processed form in the solar cell. In addition, solubility in customary process solvents is relatively low, which leads to a correspondingly low degree of pore filling. Along with stability issues, the high cost due to a complicated synthetic route and the high purity that is required (sublimation grade) in order to have good performance have been the main drawbacks for commercial applications of solid-state solar cells.

Due to the tedious multi-step synthesis of spiro-OMeTAD, which makes it prohibitively expensive and cost-ineffective, as well as the necessary high-purity sublimation-grade spiro-OMeTAD required to obtain high-performance devices, there is a huge interest in development of novel small-molecule organic semiconductors.

As such, there have been attempts to find an alternate organic HTM having higher charge carrier mobility and matching HOMO (highest occupied molecular orbital) level to replace spiro-OMeTAD. So far, although a large number and different types of HTMs were reported reaching efficiency of 16-19%, only very few candidates have showed PCE values over 19%, mainly because of the additional interaction associated with improving the hole transfer at the HTM/perovskite interface.

Thus, dispiro-oxepine/dispiro-thiamine derivatives for optoelectronic semiconductors solving the aforementioned problems are desired.

DISCLOSURE OF INVENTION According to an embodiment, a dispiro-oxepine derivative for optoelectronic semiconductors includes a compound of formula (I):

where R is hydrogen, perfluoroalkyl, or

where «=1-18; and wher

According to an embodiment, a dispiro-oxepine derivative for optoelectronic semiconductors includes a polymeric compound of formula (II):

where X is selected from one of the following polymeric compounds:

where Ar is

An optoelectronic semiconductor can include an electron transporting material (ETM) infiltrated with a perovskite absorbing material and a coating of the dispiro-oxepine derivative according to the present subject matter disposed on the ETM.

These and other features of the present disclosure will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a reaction scheme for the synthesis of dispiro-oxepine derivatives as a single molecule or monomeric form for optoelectronic semiconductors, also referred to herein as DTDOF.

Fig. 2 is an alternative reaction scheme for the synthesis of dispiro-oxepine derivatives as a polymeric form for optoelectronic semiconductors, also referred to herein as Poly-DTDOF. BEST MODE(S) FOR CARRYING OUT THE INVENTION

The dispiro-oxepine derivatives for optoelectronic semiconductors provide compounds that serve as an efficient hole transporting material when applied as a coating on an electron transporting material infiltrated with a perovskite absorbing material to form semiconductors for perovskite solar cells and other optoelectronic devices. The dispiro- oxepine derivatives, also referred to as "DTDOF" and "poly-DTDOF" herein, can include a dispiro-tri-dithienoe-oxepine-flourene (DTDOF) moiety. The dispiro-oxepine derivatives include a compound of Formula I (DTDOF), Formula II (Poly-DTDOF), and Formula III (DDOF), shown below:

where R is hydrogen, C1-C18 alkyl, C1-C18 perfluoroalkyl, or

where «=1-18; and where Ar i

where X is selected from one of the following polymeric compounds:

According to an embodiment, a dispiro-oxepine derivative for optoelectronic semiconductors includes a compound of formula (III):

Formula III where Ar is

"Hole transport material", "hole transporting material", "charge transporting material", "organic hole transport material", "inorganic hole transport material", and the like as used herein, refer to any material or composition wherein charges are transported by electron or hole movement (electronic motion) across the material or composition. The "hole transport material" is thus an electrically conductive material. Such hole transport materials, etc., are different from electrolytes, as charges are transported by diffusion of molecules in electrolytes.

The term "perovskite", as used herein, refers to the "perovskite structure" and not specifically to the perovskite material, CaTi0₃. As used herein, "perovskite" encompasses and preferably relates to any material that has the same type of crystal structure as calcium titanium oxide and other materials in which the bivalent cation is replaced by two separate monovalent cations.

The dispiro-oxepine derivatives for optoelectronic semiconductors provide a hole transporting material comprising at least one compound selected from the group consisting of a compound according to Formula I, a compound according to Formula II, and a compound according to Formula III. The dispiro-oxepine derivatives for optoelectronic semiconductors may be used to make an optoelectronic and/or photoelectrochemical device. The optoelectronic and/or photoelectrochemical device may be an organic photovoltaic device, a lasing device, a light emitting device, a photo detection device, a photovoltaic solid state device, a p-n heterojunction, silicon tandem solar cell, an organic solar cell, a dye sensitized solar cell, a solid state solar cell, a phototransistor, or an OLED. The optoelectronic and/or photoelectrochemical device may be a solid-state solar cell comprising an organic-inorganic perovskite as sensitizer under the form of a layer. The dispiro-oxepine derivatives for optoelectronic semiconductors can be used as a tuner of a HOMO level based on the presence of thiophene groups.

The dispiro-oxepine derivatives with and without dopant can provide both effective charge extraction (HTM function) and photocurrent enhancement (passivation of the perovskite layer, good electron transmission performance and cavity transmission performance) in a solid-state photovoltaic device and improve the PCE of optoelectronic and/or photoelectrochemical devices, particularly optoelectronic and/or photoelectrochemical devices comprising perovskite pigment as a sensitizer.

The optoelectronic and/or photoelectrochemical device may have a conducting support layer, a surface-increasing scaffold structure, an n-type semiconductor, a light- harvester layer or a sensitizer layer, a hole transporting layer, and a counter electrode and/or metal layer. The metal layer may be doped, as well as the n-type semiconductor. A conductive layer comprising a conductive material may be present between the hole transporting layer and the counter electrode and/or metal layer. The hole transporting layer may be provided on the sensitizer layer and is between the sensitizer layer and the conducting current providing layer, if present, or the counter electrode and/or metal layer. Further layers may be present.

The optoelectronic and/or photoelectrochemical device may comprise a combination of two or more compounds of the dispiro-oxepine derivatives for optoelectronic semiconductors as hole transporting material. The hole transporting layer may comprise the combination of two or more compounds.

The optoelectronic and/or photoelectrochemical device may comprise a hole collector layer, a conductive layer, an electron blocking layer, a sensitizer layer and a current collector layer, wherein the hole collector layer is coated by the conductive layer; and wherein the electron blocking layer is between the conductive layer and the sensitizer layer, which is in contact with the current collector layer. The hole collector layer comprises a hole transporting material comprising at least one compound of the dispiro-oxepine derivatives for optoelectronic semiconductors according to Formula I, Formula II , and/or Formula III.

The conductive material may be selected from one or more conductive polymers or one or more hole transporting materials. Examples of such materials may include poly(3,4- ethylenedioxythiophene) :poly(styrenesulfonate) (PEDOT:PS S) , poly(3 ,4- ethylenedioxythiophene):poly(styrenesulfonate):grapheme nanocomposite (PEDOT:PSS:graphene), poly(N-vinylcarbazole) (PVK) and sulfonated poly(diphenylamine) (SPDPA), preferably PEDOT:PSS, PEDOT:PSS:graphene and PVK, more preferably PEDOT:PSS. Other suitable conductive polymers may include polyaniline, polypyrrole, polythiophene, polybenzene, polyethylenedioxythiophene, polypropylenedioxy-thiophene, polyacetylene, and combinations of two or more of the aforementioned, for example. Alternatively, a transparent polymer film may be used, such as tetraacetyl cellulose (TAC), polyethylene tereph-thalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphe-nylenesulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyestersulfone (PES), polyimide (PI), polyetherimide (PEI), polycycloolefin such as polynorbornene, or brominated phenoxy resin. Polymer films are preferred, in particular PET, PEN, and polynorbornene. The conducting support layer is preferably substantially transparent. "Transparent" means transparent to at least a part, preferably a major part, of the visible light. Preferably, the conducting support layer is substantially transparent to all wavelengths or types of visible light. Furthermore, the conducting support layer may be transparent to non-visible light, such as UV and IR radiation.

The conducting support layer may provide the support layer of a photovoltaic solid- state device. Preferably, the optoelectronic and/or electrochemical device is built on the support layer. The support of the device may be also provided on the side of the counter electrode. In this case, the conductive support layer does not necessarily provide the support of the device, but may simply be or comprise a current collector, for example, a metal foil.

The conducting support layer preferably functions and/or comprises a current collector, collecting the current obtained from the device. The conducting support layer may comprise a material selected from indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), ZnO-Ga₂(¾, ΖηΟ-Αΐ₂θ₃, tin oxide, antimony-doped tin oxide (ATO), SrGe0₃ and zinc oxide, preferably coated on a transparent substrate, such as plastic or glass. In this case, the plastic or glass provides the support structure of the layer, and the cited conducting material provides the conductivity. Such support layers are generally known as conductive glass and conductive plastic, respectively, which are thus preferred conducting support layers. The conducting support layer comprises a conducting transparent layer, which may be selected from conducting glass and from conducting plastic.

Suitable inorganic electron-transport materials are semi-conductive metal oxides, including oxides of titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, cesium, niobium or tantalum. Furthermore, oxide- based semiconductors, such as may be used, wherein M and M are,

independently of each other, a metal atom, O is an oxygen atom, and x, y, and z are numbers (including 0). Examples are

and zinc stannate. These semiconducting metal oxides can act as a scaffold structure in the solar cell.

The surface-increasing scaffold structure is provided on the conducting support structure or on a protective layer that may be provided on the scaffold structure. The surface- increasing scaffold structure is nanostructured and/or mesoporous.

The scaffold structure is made from and/or comprises a metal oxide. For example, the material of the scaffold structure is selected from semiconducting materials, such as Si, Ti0₂,

GaP, InP, GaAs, CuInS₂, CuInSe₂, and combinations thereof. Preferred semiconductor materials are Si, Ti0₂, Sn0₂, ZnO, W0₃, Nb₂0₅, and SrTi0₃, for example.

There may be one or more intermediate layers between the scaffold structure and the conductive support. Such intermediate layers, if present, would preferably be conducting and/or semiconducting.

The sensitizer layer of the optoelectronic and/or photoelectrochemical device comprises at least one pigment, which may be organic, inorganic, organometallic and organic-inorganic pigments, or a combination thereof. The sensitizer is preferably a light absorbing compound or material. Preferably, the sensitizer is a pigment, and most preferably the sensitizer is an organic-inorganic pigment.

The sensitizer layer or light-harvester layer may comprise one or more pigments of the group consisting of organometallic sensitizing compounds (phthalocyanine derived compounds, porphyrine derived compounds), metal-free organic sensitizing compounds (diketopyrrolopyrrole (DPP)-based sensitizer), inorganic sensitizing compounds such as quantum dots, Sb₂S₃ (Antimony sulfide, for example in the form of thin films), aggregates of organic pigments, nanocomposites, in particular, organic-inorganic perovskites, and combinations of the aforementioned.

The optoelectronic and/or photoelectrochemical device may be selected from a photovoltaic solid-state device or a solar cell comprising an organic-inorganic perovskite as sensitizer under the form of a layer. The perovskite structure has the general stoichiometry WMX₃, where "W" and "M" are cations, and "X" is an anion. The "W" and "M" cations can have a variety of charges, and in the original Perovskite mineral (CaTi0₃), the W cation is divalent and the M cation is tetravalent.

The light-harvester layer or the sensitizer layer may comprise, or consist of, or be made of an organic-inorganic perovskite. The organic-inorganic perovskite is provided under a film of one perovskite pigment or mixed perovskite pigments or perovskite pigments mixed with further dyes or sensitizers. The sensitizer layer may comprise a further pigment in addition to the organic-inorganic perovskite pigment, the further pigment selected from an organic pigment, an organometallic pigment, or an inorganic pigment. The perovskite formulae may include structures having three (3) or four (4) anions, which may be the same or different, and/or one or two (2) organic cations, and/or metal atoms carrying two or three positive charges, in accordance with the formulae presented elsewhere herein.

Photovoltaic technology is one of the most effective approaches to utilize solar energy, which directly converts sunlight into electricity. The dispiro-oxepine derivatives for optoelectronic semiconductors also provide a new hole transporting material allowing tuning of the HOMO level and having a positive impact on the sensitizer through its passivation to improve and provide higher PCE to photovoltaic devices comprising perovskite, as well as to other optoelectronic devices, for example, Organic Light Emitting Diodes (OLED) and Field Effect Transistors (FET).

The dispiro-oxepine derivatives for optoelectronic semiconductors provide an efficient solar cell, which can be rapidly prepared in an efficient way, using readily available or low-cost materials, such as conductive material, and using a short manufacturing procedure based on industrially known manufacturing steps, keeping the material costs and the material impact on the environment very low.

The dispiro-oxepine derivatives for optoelectronic semiconductors relate to certain organic compounds, as well as their use as hole transport materials with and without dopant. In this regard, these compounds may be used to tune HOMO levels in optoelectronic and/or electrochemical devices, such as lasing, light emitting devices, and can be used for photo detection, particularly in solar cells and solid-state solar cells, including tandem cell applications comprising these compounds. The dispiro-oxepine derivatives for optoelectronic semiconductors may be used as hole transporting material and may function as hole injection materials to bring holes extracted from a sensitizer to the hole collector of a photovoltaic device, e.g., a solid solar cell. The dispiro-oxepine derivatives for optoelectronic semiconductors are able to passivate the sensitizer or the sensitizer layer and to improve the performance and the efficiency of such a device, and in particular an optoelectronic and/or photoelectrochemical device comprising an organic-inorganic perovskite as sensitizer.

The dispiro-oxepine derivatives for optoelectronic semiconductors of Formula I, Formula Π, and Formula III can be synthesized using the synthetic routes depicted Figs. 1 and 2.

Perovskite solar cells including one or more of the dispiro-oxepine derivatives of Formula I, Formula II, and Formula III can provide a power conversion efficiency (PCE) value of greater than about 20%, and a stability of greater than about 500 hours, e.g., over 1000 hours. For example, compounds of Formula I (where R=H) can provide a PCE that is greater than 20%. Compounds of Formula I (where R=C1-C18) can have a stability that is greater than 500 hours. The dispiro-oxepine derivatives for optoelectronic semiconductors of Formula I, Formula II, and Formula III can be a low cost HTM and a suitable replacement for spiro-OMeTAD.

The dispiro-oxepine derivatives for optoelectronic semiconductors will now be illustrated by the following example, which do not limit the scope defined by the appended claims.

Example 1

Synthetic route for preparing dispiro-oxepine derivatives (Compound DTDOF) The dispiro-oxepine derivatives were prepared in accordance with the reaction scheme provided in Fig. 1. To a solution of compound 1 l(equiv) in 50 mL of dry THF at - 78 °C under argon atmosphere, n-BuLi (2.1 equiv) was added dropwise. After 2 hours at the same temperature, 2,7-dibromofluorenone ( 2.5 equiv) in THF (50 mL) was added to the mixture dropwise, and the solution was warmed to room temperature and stirred overnight. The mixture was washed with water, extracted with DCM, and the combined organic phases were dried over MgSCU. The solvent was evaporated and the crude product was precipitated in ethanol to afford a white solid which was used in the next step without further purification. The obtained solid was dissolved in boiling acetic acid (100 mL), and 1 mL of concentrated hydrochloric acid were added. After refluxing for 2 hours, the mixture was washed with water and extracted with DCM, and the combined organic phases were dried over MgS0₄. This crude residue was purified by flash chromatography with pure 20 % DCM in hexane to afford compound 2 (1.4 g, 41%).

In a 50 mL Schlenk-tube, 400 mg of compound 2 (1 equiv), 560 mg commercially available 4,4'-dimethoxydiphenylamine (5 equiv), and 280 mg t-BuONa (6 equiv) were dissolved in 20 mL dry toluene and degassed for 20 minutes with N₂. After the addition of 70 mg Pd₂dba3 (0.075 mmol, 15%) and 70 mg Xphos (0.15 mmol, 30%), the reaction was refluxed overnight. The reaction was then diluted with DCM and flashed through a plug of MgS0₄ to remove inorganic salts and metallic palladium. This crude residue was purified by flash chromatography with 30% THF in hexane. Isolated compound was dissolved in THF and dropped into MeOH. The precipitate was collected by filtration, washed with MeOH and dried. 420 mg (60 % yield) of pale yellow solid was obtained to afford compound 3.

Example 2

Synthetic route for preparing Poly-DTDOF HTM materials

The HTM materials were prepared in accordance with the reaction scheme provided in Fig. 2. Compound 1 was dissolved in dry THF under nitrogen and n-BuLi was added dropwise at -78 °C. After 30 minutes of stirring, trimethyl tin chloride was added slowly at - 78 °C, then warmed to room temperature, extracted with ether, and dried in MgS0₄ to obtain compound 2. Compound 2, without purification, was used for the next reaction. Compounds 2 and 3, and Pd catalyst in dry toluene were degassed and refluxed under nitrogen for 1 day, then warmed, extracted, and dried over MgS0₄. The obtained compound 4 was further purified by column chromatography, Yield 60%.

It is to be understood that the dispiro-oxepine derivatives for optoelectronic semiconductors are not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed dispiro-oxepine derivatives for optoelectronic semiconductors.

Claims

CLAIMS We claim:

1. A dispiro-oxepine derivative for optoelectronic semiconductors, comprising a compound of the formula:

where R is hydrogen, C1-C18 alkyl, C1-C18 perfluoroalkyl, or where

where Ar

2. The dispiro-oxepine derivative for optoelectronic semiconductors, according to claim 1, wherein

3. The dispiro-oxepine derivative for optoelectronic semiconductors, according to claim 1, wherein R= H.

4. A semiconductor material for optoelectronic devices, comprising: an electron transporting material (ETM) infiltrated with a perovskite absorbing material; and

a coating disposed on the ETM material, the coating including the compound according to claim 1.

5. An optoelectronic device, comprising:

a hole collector layer;

a conductive layer;

an electron blocking layer;

a sensitizer layer; and

a current collector layer, wherein

the hole collector layer is coated by the conductive layer,

the electron blocking layer is between the conductive layer and the sensitizer layer, and

the hole collector layer includes at least one compound of the formula:

where R is hydrogen, C1-C18 alkyl, C1-C18 perfluoroalkyl, or (CH₂)„-(CF₂)„-F where «=1-18; and where Ar

6. The optoelectronic device according to claim 5, wherein R= C1-C18 alkyl.

7. The optoelectronic device according to claim 5, wherein R= H.

8. A dispiro-oxepine derivative for optoelectronic semiconductors, comprising a polymeric compound of the formula:

where X is selected from one of the following polymeric compounds:

9. A semiconductor material for optoelectronic devices, comprising: an electron transporting material (ETM) infiltrated with a perovskite absorbing material; and

a coating disposed on the ETM material, the coating including the compound according to claim 8.

10. An optoelectronic device, comprising:

a hole collector layer;

a conductive layer;

an electron blocking layer; a sensitizer layer; and

a current collector layer, wherein

the hole collector layer is coated by the conductive layer,

the hole collector layer includes at least one compound according to Claim 8.

11. A dispiro-oxepine derivative for optoelectronic semiconductors, comprising a compound of the formula:

12. A semiconductor material for optoelectronic devices, comprising:

an electron transporting material (ETM) infiltrated with a perovskite absorbing material; and a coating disposed on the ETM material, the coating including the compound according to claim 11.

13. An optoelectronic device, comprising:

a hole collector layer;

a conductive layer;

an electron blocking layer;

a sensitizer layer; and

a current collector layer, wherein

the hole collector layer is coated by the conductive layer,

the electron blocking layer is between the conductive layer and the sensitizer layi the hole collector layer includes at least one compound according to Claim 11.