JPS59168678A - Reflection checking film forming composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition suitable for manufacture of a solar cell having high conversion efficiency according to the simultaneous calcination method by a method wherein the composition having a metal complex containing an alkoxy group as a ligand, metal nitrate and a solvent as indispensable components is used. CONSTITUTION:A composition having a compound expressed by M1(OR)n(L)a-n of a general formula, or the hydrolytic condensation compound thereof, metal nitrate M2(NO3)b and a solvent as indispensable components is used. Provided that, M1 in the formula is a metal of any one of Zn, Al, Ga, In, Ti, Zr, Sn, V, Nb, Ta, Mo, W, and R is an alkyl group of 1-18 of the number of carbon, L is a negatively ionized organic ligand, (a) is the atomic value of M1, (n) is the integer of 1<=n<a, M2 is a metal of any one of Zn, Cr, Fe, Co, Ni, Cu, Al, Ga, In, Y, La, Ce, and (b) is the atomic value of M2. A composition blended with Ti(OC3H7)2(CH3COCHCOCH3)2, Cr(NO3)3.9H2O and ethyl cellusolve is used, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION Second, regarding the composition for forming an antireflection film, it is possible to improve conversion efficiency by preventing surface reflection of incident light. Therefore, a method is generally adopted in which a metal oxide thin film is formed on the light-receiving surface of a silicon substrate on which a pH junction is formed. Conventional methods (A) are used to form metal oxide thin films.
Vacuum evaporation method, (b) Spack method, (c) CVD method, etc.)
Methods such as a coating method (a method in which a metal complex is coated and then baked to form a metal oxide thin film) are used. Among these methods, (a) and (b) use a vacuum system and have relatively low productivity, and Qυ has the problem of difficulty in controlling the film thickness. Although it is a relatively easy method to control film thickness with excellent properties, both (a) and (a)
When an anti-reflection film is formed on the entire surface of the light-receiving surface, it is necessary to pattern-etch the anti-reflection film in order to form a current collecting electrode for extracting current.

In order to improve this, the following method can be considered.

That is, a metal complex coating film is formed on a PN junction forming substrate by a coating method, and then this is dried to form a metal complex dry coating film 3. Next, after pattern-printing the Ag paste for the current collector electrode using a screen printing method, the metal complex coating film and the Ag paste are simultaneously fired to form the anti-reflection film and the Al electrode at once, and to bond the Ag electrode and silicon together. This is a method of making contact.

This method can (1) form an antireflection film and an Ag electrode in one firing; (21J! Resist coating, exposure, development, etching,
It has the advantage of not requiring a series of steps such as resist removal, and has the potential to significantly streamline the manufacturing process.

However, solar cells manufactured by the above-mentioned co-firing process using a known composition for forming an anti-reflective film have a high series resistance and a small fill factor because the contact resistance between the Al electrode and silicon is not low enough. The conversion efficiency is not fully satisfactory.

For example, Ti (QC4B, ), and CH3C0CE,
Mixed liquid of COCH3 and C4H, OH (JP-A-56-6
0068), or in the general formula M(OR) 4 (in the formula M
is 0~100% Ti, 0~25% Si, 0~
It forms an alkoxide with 100% Tα or 15% or less of metal ions, where L is the valence of H)
A solar cell manufactured by the above-mentioned co-firing method using a mixed solution of alkoxide, water, alcohol, and acid represented by (JP-A-55-25487) etc. as an antireflection film forming composition has an Al electrode and a silicon The contact resistance with A,! is approximately 0,3Ω crn2, directly on the silicon. 7
There is a problem that the cost is about one order of magnitude higher than when electrodes are formed.

If this contact resistance is high, the fill factor in the IV characteristic of the solar cell becomes small, and only a solar cell with low conversion efficiency can be obtained.

The purpose of the present invention is to form an antireflection film containing a metal complex containing as a ligand, a metal nitrate, and a solvent as essential components, which are suitable for manufacturing solar cells with high conversion efficiency by the above-mentioned co-firing method. When printing the monthly paste, the metal complex dry coating must be sufficiently cured. If the coating film is not sufficiently cured, it will be damaged during printing.

It is most effective to use a metal alkoxide as the metal complex that becomes a sufficiently hardened metal complex dry coating upon drying. The metal alkoxide is represented by the general formula M(OR)TL (where M is a metal ion, R is an alkyl group, and R is a valence of H). This metal alkoxide coating film is easily hydrolyzed by moisture in the air and hardens (formula (1)).

O 2M (OR) “-Y → (RO) rL-+ MOM (OR
)n-'+2ROH M (01,) Yodo (RO) rLM 壬0JQOR), -J
20M (OR) rb-1 MO, /2 (1) However, when using a metal alkoxide whose general formula is represented by M (OR), that is, a metal complex containing only an alkoxy group as a ligand, (The IT-type hydrolysis reaction progresses too much, and the coating film becomes too hard. If the coating film becomes too hard, it becomes difficult for the Ag paste to penetrate through firing, and in the formed solar cell, the contact resistance between the Al electrode and the silicon substrate will be measured.

Therefore, in the present invention, in order to appropriately control the hydrolysis reaction of formula (1), a method is proposed in which a part of the alkoxy ligand is replaced with an organic ligand that forms a non-hydrolyzable bond with a metal ion. It was adopted. Compounds suitable as organic ligands for this purpose include β-diketone anions whose general formula is represented by R, COCHCOR2, and carboxylic acid anions whose general formula is represented by RCOO. Such a metal complex has M+ (OR
) rL (L) ct-y+, (J+ is a metal ion, OR is an alkoxy group, L is an organic ligand that forms a non-hydrolyzable bond with the metal ion, α is the valence of Ml) ,
le is 1≦ru (an integer of α).

As a β-diketone anion, CM3C0CHCO
Examples include CH3°C, H70COCH, and CM2Coo.

Furthermore, instead of M,C0R)n(L)a-n, a hydrolysis condensation compound of this complex, such as (m is an integer), may be used to appropriately control the hydrolysis reaction. is possible.

However, when a solar cell is manufactured using only a metal complex containing an alkoxy group as described above, the contact resistance between the AI electrode and Si is about 0.6Ω, and further improvement is required for practical use.

The present invention provides the above-mentioned composition for forming an antireflection film.
It is characterized by using a solution containing M+(OR)rL(L)α-l or its hydrolyzed condensation compound, a metal nitrate, and a solvent as essential components.

That is, the inventors have found that by adding metal nitrate, the hydrolysis reaction of formula (1) can be maintained at an ideal level, and the contact resistance can be lowered by about 19%.

As a metal nitrate that can be used, ZnCNo5
)t, crcNos)s pg CNOs)
s, co(A'0s)t.

Ni (#0s)z, cwcNOs)2. pa
(#03)3, Ga(NOs)s.

IrLC7VOs)m, Y(J'VOs)s,
L”(7vOs)s,”(NOx)g.

Examples include. It is also possible to use hydrates of these metal nitrates, which are included in the present invention.

The above-mentioned metal nitrates are easily soluble in organic solvents such as alcohol and cellosolve, and are compounds that can be applied to form a uniform, high-quality coating film without clouding. As a result of the inventor's studies, it has become clear that among metal nitrates, the lowest contact resistance (0.03 Ωcrn) can be obtained especially when chromium nitrate is used.

Solvents for dissolving the metal complex containing the alkoxy group and metal nitrate to form a homogeneous solution include cellosolves such as ethyl alcohol, isopropyl alcohol tx, t(D alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc.). are suitable, but other solvents may be used provided they dissolve the solid components.

The molar ratio of the metal nitrate to J'+ (OR)+z (L)α-1 or its hydrolysis condensation compound is preferably 0.1 to 1. If this ratio is smaller than 0.1, the effect of reducing contact resistance will be small, and if it is larger than 1, the coating film will be difficult to dry and will be damaged when pattern-printing the Al paste for electrodes.

The proportion of solid components in the total is 5 to 50 wt%
is desirable. If it is less than 5%, the coating film will be too thin, and if it is more than 50%, the liquid will become viscous and difficult to coat.

Methods of coating on silicon substrates include spear f coating,
Roll coating, screen printing, etc. are applicable. When coating by screen printing, a thickener such as nitrocellulose may be added to the composition for forming an antireflective film of the present invention to adjust the viscosity to a value suitable for screen printing.

The metal paste for electrode formation is preferably an Al-based paste containing Af powder as a main component, powders such as Ti, Ni, Mg, etc., and PbO-B, 03-5in2 glass frit as subcomponents.

Simultaneous firing of metal complex coating film and electrode paste is performed at 500℃~
Preferably, it is carried out at a temperature of 800°C.

When the temperature is lower than 500°C, the organic components of the metal complex are insufficiently decomposed, and leakage is likely to occur when the temperature is higher than 800°C.

In addition, the above-mentioned metal complex is added at a concentration of 2mM or more, for example, Ti
(QC,H,)t (CM, C0CHCOCH,),
and Al ((JCIH5)2(0COCsHt)), and chromium nitrate and aluminum nitrate can also be used together and are within the scope of the present invention Examples 1 to 26 Junction-forming silicon for solar cells As a substrate, P silicon substrate (resistivity 1-50, diameter 6 inch round wafer)
A pN layer with a depth of 0.3 to 1.5 μm (specific resistance approximately t5×10−”Ωcrn) was formed on one side of the pN layer using the ion implantation method, and a P+ layer with a depth of 1 to 2 μm was formed on the other side using the M diffusion method. A bonding silicon substrate 1 was used.

The compositions shown in Table 1 were prepared as antireflection film forming compositions. This composition was applied to the PN junction forming silicon substrate 1.
The 11+ layer was coated by spin coating. The rotation speed and rotation time were approximately 300 rpm and 60 seconds, respectively. Next, the coating film was dried at about 100°C for 10 minutes, and the anti-reflection dry coating film 2
I got it.

On the other hand, an Al-based paste for electrode formation was prepared by the following method. Ag powder 10Li- with a particle size of 1 μm or less, Ti powder 1y- with a particle size of 2 μm or less with a stabilized surface, and pho-B,
O, -Sin and 0.5y-based glass frit were weighed. A viscous liquid prepared by dissolving 10 parts by weight of ethyl cellulose in 90 parts by weight of α-terpineol was added to the mixture and thoroughly kneaded to obtain a viscosity of about 200 poise (shear rate 100/
An Ag paste for electrode formation was prepared. This paste was screen printed on a bonded silicon substrate on which the antireflection film forming composition described above had been applied and dried.

The light-receiving surface printed electrode 3 and the back surface printed electrode 4 were formed by screen printing in a comb-shaped pattern on the first layer and in a solid pattern on the p+ layer, and were dried at 150° C. for 1.0 minutes. Next, this substrate was baked at 600° C. for 10 minutes in a nitrogen gas atmosphere containing 50 ppm of oxygen to form an antireflection film 5.
A light-receiving surface electrode 6 and a back surface electrode 7 were obtained.

Current-voltage characteristics (1
-V% property) and short circuit current density.

The open circuit voltage 1 fill factor, conversion efficiency, etc. were measured.

Additionally, contact resistance was measured separately. short circuit current density,
The open-circuit voltage is approximately 28
mA/cm, approximately o, 5 qV. The characteristic value is the first
Shown in the table. Other characteristic values are shown in Table 1. As can be seen from Table 1, when the composition of the present invention is used, the contact resistance is 0.03 to 0.09Ω-2 and the fill factor is 0.
．． 61~0.81, conversion efficiency is 10.8~13.6
%, and it was possible to significantly improve the properties compared to when known compositions were used (Ratio Examples 1 to 4).

Among the examples, the best results were obtained in Examples 14 to 24, that is, when a paraboloid containing Cγ(7vOs)m·9H10 as the metal nitrate was used.

Examples 27 to 31 As a composition for forming an antireflection film, Tz ((7('s H,)t (CHs C0CHC
OCHs)t.

Cr(NOs)a.9B,0 and ethyl cellosolve were prepared in the proportions shown in Table 2. Using this composition, solar cells were produced in the same manner as in Examples 1 to 26.

Table 2 shows the characteristics of the obtained solar cell.

Cr(A'(7s)a・9H70 Ti (QC3M,)2(CH,C0CHCOCH,)
It can be seen that the contact resistance value is saturated when the blending molar ratio to , is 0.1 or more. On the other hand, when this ratio is greater than 1, the drying of the coating film is insufficient, and when the formed antireflection film was observed under a microscope, it was seen that there were marks from the screen plate.

By using oxides, antireflection films and electrodes for solar cells can be formed using a method that is simpler than conventional processes, that is, a method that does not require steps such as resist formation, etching, and resist removal. Moreover, it is possible to form the antireflection film and the electrode all at once by firing twice, and the properties as a solar cell are also very good.

Therefore, according to the present invention, it is possible to manufacture an energy-saving and long-lasting solar cell, and the cost can be reduced, so that the present invention has great industrial significance.

[Brief explanation of the drawing]

Figure 1 shows a cross-sectional view of a solar cell at each step when the solar cell is manufactured using the composition for forming an antireflection film of the present invention. 1: PN junction formed silicon substrate 2: Antireflection dry coating film 6: Light-receiving surface printed electrode 4: Back surface printed electrode 5: Antireflection film FIG. Yu) [== de' 292 Yoshida-cho, Totsuka-ku, Yokohama, Hitachi, Ltd., Institute of Industrial Science, 72) Inventor: Tadashi Saito, Kokubunji City, Higashi Koigakubo-chome, 280, Hitachi, Ltd. Central Research Laboratory, Plastic Co., Ltd. Kunihiro Matsukuma 3-1-1 Saiwaimachi, Hitachi City Stock % Formula % Amendment to procedures within Tachiharamachi Electronic Industry Co., Ltd. (voluntary) Case description 1982 Patent Application No. 42101'; 3 Inventions c
r> Name Person correcting the composition for forming an anti-reflective film/Relationship with the matter Application Person name I
iH: L 51 o) Ino Shikikai Month ■
Subject of person's amendment Supplementary column for the detailed explanation of the invention in the specification iE content description page 14, line 17, ``Comparative example'' has been changed to ``Comparative example''
Correct.

Claims (1)

[Claims] 1. The general formula is “+ (OR)n(L) a-n (M,
is Zn,M. Ga, In, "l'i, Zr, Sn, V, Nh, Ta
, No., metal selected from IP, R has 1 to 18 carbon atoms
A compound represented by an alkyl group, L is an anionic organic ligand, α is the valence of Ml, and L is 1≦L (an integer of α),
or these hydrolysis condensation compounds and metal nitrate mt
Cyos) b(&, is Zn, Cr. Fg, Co, #Otsu, Ctb, lJ,, Gα, I
A composition for forming an antireflection film, which contains a metal selected from L, Y, Lα, and Ct (b is the valence of M2) and a solvent as essential components. 2. The composition for forming an antireflection film according to claim 1, wherein the anionic organic ligand is a β-diketone anion. 6. The composition for forming an antireflection film according to claim 1, wherein the anionic organic ligand is a carboxylic acid anion. 4. The composition for forming an antireflection film according to claim 1, wherein the metal nitrate is chromium nitrate. 5゜ Metal nitrate and's (OR)yc (L) a-
The mixing molar ratio of n or its hydrolyzed condensation compound is 0.
The composition for forming an antireflection film according to claim 1, characterized in that the ratio is 1:1 to 1:1. & The total weight of metal nitrate and MI COR)n CL) α-U or its hydrolyzed compound is 5 to 50 wt.
% of the composition for forming an antireflection film according to claim 1.