KR20110105396A - Solution for increasing wafer sheet resistance and/or photovoltaic cell power density level - Google Patents

Abstract

The present invention provides a thin film amorphous or single- or poly-crystalline silicon wafer substrate for a photovoltaic cell having a pn- or np bond and at least one of a partial phosphosilicate or borosilicate glass layer on its upper surface. And a method for processing to increase at least one of surface resistance and (b) power density levels of the photovoltaic cell made of the wafer. The treatment solution comprises one or more tetraalkylammonium hydroxides, acetic acid, one or more nonionic surfactants, one or more metal chelate reagents, a metal free source of ammonium ions, a metal free of fluoride ions, mixed with an oxidant solution and optionally water Source, and an acidic treatment solution of a buffered oxide etch (BOE) solution of water.

Description

SOLUTION FOR INCREASING WAFER SHEET RESISTANCE AND / OR PHOTOVOLTAIC CELL POWER DENSITY LEVEL}

The present invention provides a thin film amorphous or single- or poly-crystalline silicon wafer substrate for a photovoltaic cell having an acidic treatment composition and at least one pn- or np bond and a partial phosphosilicate or borosilicate glass layer on its top surface. It relates to the use of such an acidic treatment composition in a method of processing to provide increased sheet resistance and / or power density of the photovoltaic cell made of the wafer.

Silicon-based solar cells, or photovoltaic cells, require some processing steps to convert incident light into current. One of these steps involves the generation of emitters, which can be most commonly performed by thermal drive of phosphorus to boron-doped silicon wafers. This process results in the generation of so-called dead layers, which result in high recombination rates of generated charges and are detrimental to the efficiency and power density levels of solar cells. In addition, this process produces a so-called phosphosilicate glass (PSG) layer containing phosphorus, silicon and oxygen on top of the wafer and this PSG layer must be removed to proceed with cell fabrication. After the thermal drive process, the phosphorus depth profile shows a high concentration of plateau spreading from the surface to tens or hundreds of nanometers deep, depending on the process conditions. Ideally, the concentration near the surface would be high (ie 10 ^20-21 atoms / cm ³ ) in order to be able to contact the electrode well.

The main goal of polycrystalline photovoltaic manufacturers is to reduce the cost of the energy carried by their solar cells. This can generally be done in one of two ways: reduction in overall cell manufacturing cost and / or increase in solar cell conversion efficiency. In an effort to achieve the latter purpose, the current fabrication process applies post-emitter etching after phosphorus dispersion, which removes the PSG layer by dipping the wafer in HF. Previous experiments have shown that additional processing after HF-dip can result in higher cell efficiency, up to 0.3% absolute. At present, the product of Malinckrodt Baker, Inc., product PV-160, is used in this additional step. However, the use of this product generally requires processing of the wafer substrate in the heating bath of the product (above 70 ° C.).

Improved etching of the rest of the PSG layer and deeper etching of the dead layer compared to the results obtained with current PV-160 products produce higher power densities at reduced temperatures at the same or less processing time in solar cells. It is highly desirable that a composition that can be used is available.

In a first embodiment the present invention is a thin film amorphous or single- or poly-crystalline silicon wafer substrate for photovoltaic cells having a pn- or np bond and / or a partial phosphosilicate and / or borosilicate glass layer on its upper surface. For a sufficient time at a temperature sufficient to increase at least one of (a) the surface resistance of the wafer and (b) the power density of the photovoltaic cell made of the wafer.

Mixed with oxidant and optionally water in a volume ratio of oxidant / water / BOE solution of 0.01-10 / 0-100 / 1,

About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,

About 0.1 to about 5 weight percent acetic acid,

About 0.1 to about 5 weight percent of one or more nonionic surfactant,

About 0.1 to about 5 weight percent of one or more metal chelate reagents,

About 0.1 to about 20 weight percent of a metal free source of ammonium ions,

About 0.01 to about 20 weight percent of a metal free source of fluoride ions,

Remaining volume of water up to 100%

Contacting with an acidic treatment solution comprising a buffered oxide etch (BOE) solution of

A method of treating a wafer substrate for increasing at least one of (a) the surface resistance of a wafer and (b) the power density of a photovoltaic cell made of the wafer. Wafers with emitters include both p- and n- source silicon types.

The treatment can increase the surface resistance of the wafer or the power density of the photovoltaic cell, which preferably increases both. In addition, the treatment can also increase the efficiency of photovoltaic cells made from the wafer.

In a further embodiment of the invention,

Mixed with oxidant and optionally water in a volume ratio of oxidant / water / BOE solution of 0.01-10 / 0-100 / 1,

About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,

About 0.1 to about 5 weight percent acetic acid,

About 0.1 to about 5 weight percent of one or more nonionic surfactant,

About 0.1 to about 5 weight percent of one or more metal chelate reagents,

About 0.1 to about 20 weight percent of a metal free source of ammonium ions,

About 0.01 to about 20 weight percent of a metal free source of fluoride ions,

Remaining volume of water up to 100%

A mixture of a buffered oxide etch (BOE) solution of

A thin film amorphous or single- or poly-crystalline silicon wafer substrate for photovoltaic cells having a pn- or np bond and / or a partial phosphosilicate and / or borosilicate glass layer on its upper surface, (a) the surface resistance of the wafer And (b) an acidic treatment solution for treating to increase at least one of the power density of the photovoltaic cell made of the wafer. Wafers with emitters include both p- and n- source silicon types.

In all of these embodiments the gravimetric amount of tetraalkylammonium chloride in the BOE solution is preferably 0.5 to 15%, more preferably 1 to 10%, even more preferably 1.5 to 8%, most preferably 2 to 4%, Especially 3.1%.

The weight-based amount of acetic acid is preferably 0.5 to 4%, more preferably 0.8 to 3%, even more preferably 1 to 2%, most preferably 1 to 1.5%, in particular 1-2%.

For nonionic surfactants the weight-based amount is preferably 0.2 to 4%, more preferably 0.3 to 2%, even more preferably 0.5 to 1%, most preferably 0.7 to 0.9%, especially 0.8%.

The weight-based amount for the chelating reagent is preferably 0.2 to 4%, more preferably 0.3 to 3%, even more preferably 0.4 to 1%, most preferably 0.5 to 0.8%, especially 0.6%.

For the source of ammonium ions, the weight-based amount is preferably 0.2 to 10%, more preferably 0.3 to 5%, even more preferably 0.5 to 2%, most preferably 0.6 to 1%, especially 0.8%.

For the source of fluoride ions, the weight-based amount is preferably 1 to 10%, more preferably 0.5 to 5%, even more preferably 1.0 to 3%, most preferably 1.5 to 2.5%, especially 2.1%.

The treatment can increase the surface resistance of the wafer or the power density of the photovoltaic cell made from the wafer, which preferably increases both. In addition, the treatment can also increase the efficiency of photovoltaic cells made from the wafer.

In a preferred embodiment of the invention the treatment occurs at a temperature of about 20 ° C to less than 70 ° C.

In another preferred embodiment of the invention, the BOE solution has a pH of less than about 3 to 7, preferably a pH of about 3 to about 6, and more preferably has a pH of about 4.3 to about 5.

In a still further preferred embodiment of the invention, the oxidant comprises hydrogen peroxide. Generally the oxidizing agent is an aqueous solution of water and hydrogen peroxide (0.01% to 50%, more preferably 0.1% to 30%, and even more preferably in any suitable proportion, but generally in a ratio of about 6 / 10.2 to about 6/1. About 30% aqueous solution).

In another preferred embodiment of the invention, the BOE solution comprises tetramethylammonium hydroxide as tetraalkylammonium hydroxide, 3,5-dimethylhex-1-yn-3-ol as one or more surfactants, and One or more metal chelate reagents include EDTA, and the oxidant solution includes hydrogen peroxide and water.

In another preferred embodiment of the invention, the BOE solution comprises about 3.1% tetramethylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol , About 0.8% ammonium hydroxide, about 0.6% EDTA, about 91.5% water (the percentage is by weight).

In another preferred embodiment of the invention, the BOE solution is mixed with the oxidant solution at a ratio of BOE / water / hydrogen peroxide of about 1/6 / 0.2. In another preferred embodiment of the invention, the BOE solution is mixed with the oxidant solution at a ratio of BOE / water / hydrogen peroxide of about 1/6 / 0.8. In another preferred embodiment of the invention, the BOE solution is mixed with the oxidant solution at a ratio of BOE / water / hydrogen peroxide of about 1/6/1.

In yet another preferred embodiment of the present invention, the embodiment comprises one or more of the combinations of the preferred embodiments described above.

In addition, the present invention can be used at process temperatures of about 20 ° C. to about 40 ° C., lower than the current industry standard of 70 ° C.

The present invention provides a thin film amorphous or single- or polycrystalline silicon wafer substrate for a photovoltaic cell having a pn- or np bond and / or a partial phosphosilicate and / or borosilicate glass layer on its upper surface (a) wafer For a sufficient time at a temperature sufficient to increase at least one of the surface resistance of and (b) the power density of the photovoltaic cell made of the wafer.

Mixed with oxidant and optionally water in a volume ratio of oxidant / water / BOE solution of 0.01-10 / 0-100 / 1,

About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,

About 0.1 to about 5 weight percent acetic acid,

About 0.1 to about 5 weight percent of one or more nonionic surfactant,

About 0.1 to about 5 weight percent of one or more metal chelate reagents,

About 0.1 to about 20 weight percent of a metal free source of ammonium ions,

About 0.01 to about 20 weight percent of a metal free source of fluoride ions,

Remaining volume of water up to 100%

Contacting with an acidic treatment solution comprising a buffered oxide etch (BOE) solution of

A method of treating a wafer substrate for increasing at least one of (a) the surface resistance of a wafer and (b) the power density of a photovoltaic cell made of the wafer. Wafers with emitters include both p- and n- source silicon types.

The treatment can increase the surface resistance of the wafer or the power density of photovoltaic cells made from the wafer, which preferably increases both. In addition, the treatment can also increase the efficiency of photovoltaic cells made from the wafer.

Similarly, the present invention

Mixed with oxidant and optionally water in a volume ratio of oxidant / water / BOE solution of 0.01-10 / 0-100 / 1,

About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,

About 0.1 to about 5 weight percent acetic acid,

About 0.1 to about 5 weight percent of one or more nonionic surfactant,

About 0.1 to about 5 weight percent of one or more metal chelate reagents,

About 0.1 to about 20 weight percent of a metal free source of ammonium ions,

About 0.01 to about 20 weight percent of a metal free source of fluoride ions,

Remaining volume of water up to 100%

A mixture of a buffered oxide etch (BOE) solution of

A thin film amorphous or single- or poly-crystalline silicon wafer substrate for photovoltaic cells having a pn- or np bond and / or a partial phosphosilicate and / or borosilicate glass layer on its upper surface, (a) the surface resistance of the wafer And (b) an acidic treatment solution for treating to increase at least one of the power density of the photovoltaic cell made of the wafer. Wafers with emitters include both p- and n- source silicon types.

The treatment can increase the surface resistance of the wafer or the power density of photovoltaic cells made from the wafer, which preferably increases both. In addition, the treatment can also increase the efficiency of photovoltaic cells made from the wafer.

The use of an acidic treatment solution in the process of the present invention is followed by removal of phosphosilicate or borosilicate glass with HF (incomplete removal) and other HF dipping and subsequent antireflective coating (ARC), such as for example SiNxH deposition. Just before it is used on a photovoltaic wafer substrate. The process involves submerging the wafer substrate in a heating bath of the solution for a sufficient time at a temperature sufficient to increase, for example, (a) the surface resistance of the wafer and (b) the power density of the photovoltaic cell made of the wafer. Exposing to an acidic treatment solution. Contacting the wafer substrate with the acidic treatment solution is generally performed for a period of about 0.01 to about 20 minutes, preferably about 0.5 to about 5 minutes, more preferably about 1 minute. The temperature of the solution will generally be about 20 ° C to less than about 70 ° C, preferably about 20 ° C to about 60 ° C, more preferably about 20 ° C to about 40 ° C, even more preferably about 40 ° C.

Tetraalkylammonium hydroxide or a salt of the formula [(R) ₄ N ⁺ ] _p [X ^-q ] wherein each R is independently substituted or unsubstituted alkyl, preferably 1 to 22 alkyl More preferably 1 to 6, most preferably 1 carbon; X is OH or a suitable salt anion, such as carbonate, etc., p and q are equivalent and are integers of 1 to 3). It may be mentioned that it is suitable for use. Tetramethyl ammonium hydroxide and trimethyl-2-hydroxyethyl ammonium hydroxide (choline) are most preferred of these. Examples of other quaternary ammonium hydroxides that may be used include: trimethyl-3-hydroxypropyl ammonium hydroxide, trimethyl-3-hydroxybutyl ammonium hydroxide, trimethyl-4-hydroxybutyl ammonium hydroxide Lockside, triethyl-2-hydroxyethyl ammonium hydroxide, tripropyl-2-hydroxyethyl ammonium hydroxide, tributyl-2-hydroxyethyl ammonium hydroxide, dimethylethyl-2-hydroxyethyl Ammonium hydroxide, dimethyldi (2-hydroxyethyl) ammonium hydroxide, monomethyltri (2-hydroxyethyl) ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetrabutyl Ammonium hydroxide, monomethyltriethyl ammonium hydroxide, monomethyltripropyl ammonium hydroxide, monomethyltributyl ammonium hydroxide, mono Teal trimethylammonium hydroxide, monoethyl tributyl ammonium hydroxide, dimethyl diethyl ammonium hydroxide, dimethyl di-butylammonium hydroxide, etc., and mixture thereof.

The metal free source of ammonium ions can be any suitable metal free ammonium salt, such as, for example, ammonium hydroxide, ammonium fluoride, ammonium chloride, ammonium nitrate and the like, but is preferably ammonium hydroxide. The metal free source of fluoride ions can be any suitable metal free fluoride compound, such as quaternary ammonium fluoride such as, for example, hydrogen fluoride, ammonium fluoride, tetramethylammonium fluoride. Preferably the metal free source of fluoride ions is HF. In another preferred embodiment both ammonium ions and fluoride ions can be provided as one compound, ie ammonium fluoride.

The acidic treatment composition of the present invention may comprise any suitable nonionic surfactant. Among various suitable nonionic surfactants, for example, low foamed nonionic surfactants such as alkynol surfactants, fluorinated surfactants such as fluorinated alkyl alkoxylates such as Fluorad® FC-171, Fluorinated alkyl esters such as FC-430 and FC-431 and fluorinated polyoxyethylene alkanols such as fluoride® FC-170C, fatty acid esters of polyhydric alcohols, polyoxyethylene monoalkyl ethers, polyoxyethylene diols, It may be mentioned that alkylene glycol monoalkyl ethers such as siloxane type surfactants and butoxypropanol are useful in the treatment compositions of the present invention. Alkinol surfactants, in particular 3,5-dimethylhex-1-yn-3-ol (Surfynol®-61) or any other liquor, for use as a nonionic surfactant in the alkaline treatment compositions of the present invention Pynol® surfactants, fluorinated alkyl polyoxyethylene ethanol, in particular fluoride® FC-170C and alkylene glycol monoalkyl ethers, in particular butoxypropanol are preferred.

Any suitable metal chelate reagent that increases the ability of the formulation to retain metal in solution can be used in the acidic treatment compositions of the present invention. Typical examples of chelating reagents for this purpose are the following organic acids and their salts: ethylenediaminetetraacetic acid (EDTA), butylenediaminetetraacetic acid, cyclohexane-1,2-diaminetetraacetic acid (CyDTA) diethylenetriaminepentaacetic acid , Ethylenediaminetetrapropionic acid, (hydroxyethyl) ethylenediaminetriacetic acid (HEDTA), methyliminodiacetic acid, propylenediaminetetraacetic acid, nitrolotriacetic acid (NTA), citric acid, tartaric acid, gluconic acid, sacaric acid, glycerol Acids, oxalic acid, phthalic acid, maleic acid, mandelic acid, malonic acid, lactic acid, salicylic acid, catechol, 8-hydroxyquinoline, N, N, N ', N'-ethylenediaminetetra (methylenephosphonic acid) and the like.

Any suitable oxidizing agent, such as, for example, an oxidizing anion such as, for example, peroxide, nitric acid and salts thereof and nitrates, persulfates, periodates, perbromates, perchlorates, iodates, bromates of ammonium , And chlorate salts can be used. Peroxides and especially hydrogen peroxide are preferred.

Acidic treatment compositions of the invention can be prepared by mixing with the required ingredients in a suitable container to form the composition. Preferably the required components of the composition are added to the vessel in the order of base / acid / base / acid to minimize any possible heat from the reaction of the components.

However, in solar cell production the product will have to etch not only silicon oxide but also silicon and sidewalks. To achieve this, BOE is combined with hydrogen peroxide as oxidant. This means that in the subsequent process of etch-oxidation, the BOE etches the silicon oxide while the oxidant generates new silicon oxide on the surface. In addition, the oxidant oxidizes the phosphorus present in the layer, making it soluble. The etched species (including but not limited to metal impurities) are held in solution by the addition of a chelating reagent, in part, while the wettability of the surface (ie the efficiency with which the oxidant can oxidize the surface) It is improved by addition. The addition of acetic acid ensures a double buffered system that aids in process stability.

The invention is illustrated by, but not limited to, the following examples. In the examples the percentages are by weight.

Example  One

A set of 25 neighboring poly-crystalline silicon wafers of size about 15.6 x 15.6 cm ² with a thickness of about 180-200 μm was processed in industrial type in-line photovoltaic fabrication sequence. After emitter deposition and phosphorus glass removal with HF, the wafer with a partial phosphorusilicate glass layer on top of the wafer substrate was (1) acid treated solution of the invention at 40 ° C., (2) required for such a solution. Contact with no prior art PV-160 solution, or (3) no treatment solution, as a control at 70 ° C. The acidic treatment solution of the present invention comprises about 3.1% tetramethylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol, about 0.8% ammonium hydroxide BOE solution comprising lockside, about 0.6% EDTA, about 91.5% water. The BOE solution was mixed with the hydrogen peroxide oxidant solution at a ratio of about 1/6 / 0.2 BOE / water / 30% hydrogen peroxide solution. The prior art PV-160 solution was also used in admixture with the hydrogen peroxide oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6 / 0.2. The treated wafers were then subjected to wet chemical treatment in a 1% by weight HF solution at room temperature for 1 minute, followed by the usual conventional photovoltaic fabrication steps to produce the desired photovoltaic cell. The electrode firing settings were kept constant while the other group was being processed and placed in the optimal firing settings for the prior art group. Their power density levels were measured for the cells (unit mW / cm ² , defined as the product of short circuit current density and open circuit voltage, Jsc x Voc). Table 1 shows the results.

Example  2

A set of 25 neighboring poly-crystalline silicon wafers of size about 15.6 x 15.6 cm ² with a thickness of about 180-200 μm was processed in industrial type inline photovoltaic fabrication sequence. After emitter deposition and phosphorus glass removal with HF, the wafer with a partial phosphorusilicate glass layer on top of the wafer substrate was (1) acid treated solution of the invention at 40 ° C., (2) required for such a solution. Contact with prior art PV-160 solution at 70 ° C. The treatment solution of the present invention comprises about 3.1% tetramethylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol, about 0.8% ammonium hydroxide BOE solution containing Said, about 0.6% EDTA, about 91.5% water. The BOE solution was mixed with the hydrogen peroxide oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide of about 1/6 / 0.8. The prior art PV-160 solution was also used in admixture with the hydrogen peroxide oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6 / 0.2. The treated wafers were then subjected to wet chemical treatment in a 1% by weight HF solution at room temperature for 1 minute, followed by the usual conventional photovoltaic fabrication steps to produce the desired photovoltaic cell. The electrode firing settings were kept constant while the other group was being processed and placed in the optimal firing settings for the prior art group. Their power density levels were measured for the cells (unit mW / cm ² , defined as the product of short circuit current density and open circuit voltage, Jsc x Voc). Table 2 shows the results.

Example  3

A set of 25 neighboring poly-crystalline silicon wafers of size about 15.6 x 15.6 cm ² with a thickness of about 180-200 μm was processed in industrial type inline photovoltaic fabrication sequence. After emitter deposition and phosphorus glass removal with HF, the wafer with a partial phosphorusilicate glass layer on top of the wafer substrate was (1) acid treated solution of the invention at 25 ° C, 30 ° C, and 40 ° C, (2 ) Prior art PV-160 solution at 70 ° C. required for this solution, or (3) no solution as control. The acidic treatment solution of the present invention comprises about 3.1% tetramethylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol, about 0.8% ammonium hydroxide BOE solution comprising lockside, about 0.6% EDTA, about 91.5% water. The BOE solution was mixed with the hydrogen peroxide oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6/1. The prior art PV-160 solution was also used in admixture with the hydrogen peroxide oxidant solution at a ratio of BOE / water / hydrogen peroxide solution of about 1/6 / 0.2. The treated wafers were then subjected to wet chemical treatment in a 1% by weight HF solution at room temperature for 1 minute, followed by the usual conventional photovoltaic fabrication steps to produce the desired photovoltaic cell. The electrode firing settings were kept constant while the other group was being processed and placed in the optimal firing settings for the prior art group. Table 3 shows the results.

As shown in the above results, the composition of the present invention significantly increased the surface resistance and / or power density level of the cell compared to the control. By varying the mixing ratio and significantly increasing the amount of hydrogen peroxide, the compositions of the present invention showed the same or superior power density compared to PV-160. However, while the PV-160 composition requires a temperature of 70 ° C. for the above results, the composition of the present invention could do so at a temperature of 20 ° C. to 40 ° C.

While the invention has been described herein with reference to specific embodiments thereof, it is to be understood that changes, modifications and variations can be made without departing from the spirit and scope of the inventive concepts disclosed herein. Accordingly, it is intended to embrace all such changes, modifications and variations that fall within the spirit and scope of the appended claims.

Claims (23)

A thin film amorphous or single- or polycrystalline silicon wafer substrate for a photovoltaic cell having a pn- or np bond and at least one of a partial phosphosilicate or borosilicate glass layer on its upper surface, comprising: (a) the surface resistance of the wafer and (b) for a sufficient time at a temperature sufficient to increase at least one of the power densities of the photovoltaic cell made of the wafer;
Mixed with oxidant solution and optionally water at a ratio of 0.01-10 / 0-100 / 1 oxidant solution / water / BOE solution,
About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,
About 0.1 to about 5 weight percent acetic acid,
About 0.1 to about 5 weight percent of one or more nonionic surfactant,
About 0.1 to about 5 weight percent of one or more metal chelate reagents,
From about 0.1 to about 20 weight percent of ammonia ion free metal source,
About 0.01 to about 20 weight percent of a metal free source of fluoride ions,
Remaining volume of water up to 100%
Contacting with an acidic treatment solution comprising a buffered oxide etch (BOE) solution of
And processing the wafer substrate to increase at least one of (a) surface resistance and (b) power density of the photovoltaic cell. The method of claim 1, wherein the treatment occurs at a temperature of about 20 ° C. to about 70 ° C. 7. The method of claim 1 or 2, wherein the BOE solution has a pH of about 3 to about 6. 4. The method of claim 3, wherein the BOE solution has a pH of about 4.3 to about 5. The method of claim 1, wherein the oxidant solution comprises hydrogen peroxide. The 3-ol of claim 1, wherein the BOE solution comprises tetramethylammonium hydroxide as tetraalkylammonium hydroxide and 3,5-dimethylhex-1-yn-3-ol as one or more surfactants. And EDTA as one or more metal chelate reagents, wherein the oxidant solution comprises hydrogen peroxide and water. The method of claim 6, wherein the BOE solution is about 3.1% tetramethylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol, about 0.8 % Ammonium hydroxide, about 0.6% EDTA, about 91.5% water. 8. The method of claim 7, wherein the BOE solution is mixed with an oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide in the range of 1/6 / 0.2-1.0. 8. The method of claim 7, wherein the BOE solution is mixed with an oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6 / 0.2. 8. The method of claim 7, wherein the BOE solution is mixed with the oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6 / 0.8. 8. The method of claim 7, wherein the BOE solution is mixed with an oxidant solution at a ratio of about 1/6/1 of BOE / water / 30% hydrogen peroxide solution. 10. The method of claim 9, wherein said treatment occurs at a temperature of about 20 ° C to about 70 ° C. 13. The method of any one of the preceding claims, wherein the treatment further improves the efficiency of the photovoltaic cell made of the wafer. Mixed with oxidant solution and optionally water at a ratio of 0.01-10 / 0-100 / 1 oxidant solution / water / BOE solution,
About 0.1 to about 20 weight percent of at least one tetraalkylammonium hydroxide,
About 0.1 to about 5 weight percent acetic acid,
About 0.1 to about 5 weight percent of one or more nonionic surfactant,
About 0.1 to about 5 weight percent of one or more metal chelate reagents,
From about 0.1 to about 20 weight percent of ammonia ion free metal source,
About 0.01 to about 20 weight percent of a metal free source of fluoride ions,
Remaining volume of water up to 100%
A mixture of a buffered oxide etch (BOE) solution of
A thin film amorphous or single- or polycrystalline silicon wafer substrate for a photovoltaic cell having a pn- or np bond and at least one of a partial phosphosilicate or borosilicate glass layer on its upper surface, comprising: (a) the surface resistance of the wafer and (b) an acidic treatment solution for treating to increase at least one of the power densities of the photovoltaic cells made of the wafer. The acidic treatment solution of claim 14 wherein the BOE solution has a pH of about 3 to about 6. 16. The acidic treatment solution of claim 15 wherein the BOE solution has a pH of about 4.3 to about 5. 17. The acidic treatment solution of claim 14 or 15 wherein the oxidant solution comprises hydrogen peroxide. 18. The 3-ol of claim 14, wherein the BOE solution comprises tetramethylammonium hydroxide as tetraalkylammonium hydroxide and 3,5-dimethylhex-1-yn-3-ol as one or more surfactants. And, as one or more metal chelate reagents, EDTA, and wherein the oxidant solution comprises hydrogen peroxide and water. The method of claim 18, wherein the BOE solution is about 3.1% tetraalkylammonium hydroxide, about 1.2% acetic acid, about 2.1% HF, about 0.8% 3,5-dimethylhex-1-yn-3-ol, about 0.8 An acidic treatment solution comprising% ammonium hydroxide, about 0.6% EDTA, about 91.5% water. The acidic treatment solution of claim 19 wherein the BOE solution is mixed with an oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution in the range of 1/6 / 0.2-1.0. The acidic treatment solution of claim 19 wherein said BOE solution is mixed with an oxidant solution at a ratio of BOE / water / 30% hydrogen peroxide solution of about 1/6 / 0.2. 20. The acidic treatment solution of claim 19 wherein said BOE solution is mixed with an oxidant solution at a ratio of about 1/6 / 0.8 BOE / water / 30% hydrogen peroxide solution. 20. The acidic treatment solution of claim 19 wherein said BOE solution is mixed with an oxidant solution at a ratio of about 1/6/1 of BOE / water / 30% hydrogen peroxide solution.