CN100555679C - The caustic solution of CdTe thin film solar cell - Google Patents

The caustic solution of CdTe thin film solar cell Download PDF

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CN100555679C
CN100555679C CNB2008100457312A CN200810045731A CN100555679C CN 100555679 C CN100555679 C CN 100555679C CN B2008100457312 A CNB2008100457312 A CN B2008100457312A CN 200810045731 A CN200810045731 A CN 200810045731A CN 100555679 C CN100555679 C CN 100555679C
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cdte
solar cell
thin film
nitric acid
naac
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CN101335310A (en
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冯良桓
李卫
蔡亚平
武莉莉
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Sichuan University
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Sichuan University
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract

The surface corrosion of CdTe film and be equipped with the CdTe solar cell with this legal system belongs to the semiconductor device fabrication field.The mixed liquor that adopts nitric acid, glacial acetic acid, NaAc and deionized water is as corrosive liquid, and wherein, NaAc is as buffer, and is constant with the pH value that keeps solution, makes reaction more stable, and reacting by CdTe and nitric acid generates rich tellurium layer; After cleaning dried up, deposition contained Cu or does not contain the Cu back contact, deposited back electrode at last with preparation CdTe solar cell.Deposition back of the body contact material can increase near the carrier concentration of pn knot, reduces schottky barrier height, avoids directly depositing the Cu that Cu forms more complicated xThe Te structure.Adopt this method corrosion and preparation CdTe solar cell, can significantly improve the performance of solar cell, and guarantee the stable and repeated of device performance.

Description

The caustic solution of CdTe thin film solar cell
Technical field
The invention belongs to the semiconductor device fabrication field, particularly the surface corrosion of CdTe film and be equipped with the CdTe solar cell with this legal system.
Background technology
The basic structure of CdTe solar cell is: glass substrate (G)/nesa coating (T)/n-CdS (W)/p-CdTe (A)/back electrode (M), as shown in Figure 1.Back electrode often adopts metal, but the work function of CdTe higher (5.5eV) is difficult to find a kind of metal and its formation ohmic contact of high work function, thereby has greatly influenced the performance of solar cell.
At present, the way of solution is exactly earlier the CdTe film surface to be corroded, and deposits the back contact material again.Usually, corrosion of bromine methyl alcohol and the corrosion of phosphorus nitric acid are adopted in the chemical corrosion of CdTe film surface, studies show that: adopt bromine methyl alcohol corrosion CdTe solar cell, bromine often penetrates the CdTe film, even arrives the CdTe/CdS interface, in addition, bromine methyl alcohol corrosive liquid high volatility, poisonous, be unfavorable for suitability for industrialized production; Suitability for industrialized production often adopts the corrosion of phosphorus nitric acid, but weak point is to have preferential etch, particularly along the grain boundary corrosion, causes metal ion or impurity to spread along grain boundary, forms the conduction bypass.
Summary of the invention
The objective of the invention is defective and deficiency in order to solve above-mentioned existence, wet-chemical etching technology and back of the body contact technique among the CdTe solar cell preparation technology have been improved, be that isotropic etch goes out rich Te layer, and be not subjected to the influence (as the reprocessing of CdTe depositing of thin film, CdTe film) of early stage preparation technology and process, keep the integrality of crystal grain simultaneously; Deposition contains Cu or does not contain the Cu back contact (as ZnTe:Cu, HgTe:Cu, Sb subsequently 2Te 3, NiTe 2), avoid directly depositing the Cu that Cu forms more complicated xThe Te structure.
Be to realize the present invention, the corrosive liquid that technical scheme of the present invention adopts glacial acetic acid, nitric acid, NaAc and deionized water to form corrodes under suitable temperature, and then deposition contains Cu or do not contain the Cu back contact, as ZnTe:Cu, HgTe:Cu, Sb 2Te 3Or NiTe 2Deng in any, plate back electrode at last, a kind of as among Ni, Ni/Al alloy or the Au etc. is to finish preparation of devices.
In the present invention, nitric acid as oxidant, glacial acetic acid provides sour environment, and NaAc plays cushioning effect, can keep the pH value of solution constant, makes reaction more stable, and easier control is not subjected to the influence of CdTe film historical situation, and its reaction equation is as follows:
3CdTe+8HNO 3→3Te+3Cd(NO 3) 2+2NO+4H 2O (1)
CdTe+4HNO 3→Te+Cd(NO 3) 2+2NO 2+2H 2O (2)
Te has reduced the barrier height between Te and the CdTe in the CdTe solar cell, reduced contact resistance, and then has reduced the recombination current at crystal boundary, simultaneously as P +Layer, the about 0.33eV of its energy gap with the about 0.26eV of the valence band offset at CdTe interface, helps the hole and enters the Te layer by CdTe.Simultaneously, also can expand the long wave response.Because chemical corrosion can only generate rich Te layer, in order to reduce Schottky barrier, also need deposit and contain Cu or do not contain the Cu back contact, reduce interface state density, increase near the carrier concentration the pn knot, reduce schottky barrier height.Adopting above-mentioned corrosive liquid is that 30cm * 40cm CdTe polycrystal film carries out chemical corrosion to area, after the cleaning, directly plates electrode and makes the CdTe thin film solar cell, has obtained about 200 area～0.07cm 2Baby battery, its conversion efficiency is evenly distributed, and conversion efficiency＞9%; The CdTe polycrystal film of same process preparation carries out depositing back contact after the chemical corrosion, as ZnTe:Cu, plates electrode at last and makes the CdTe thin film solar cell, and photoelectric conversion efficiency on average increases by 40%～60%.Therefore, the invention has the beneficial effects as follows: adopt corrosion of this method and deposition to contain Cu or do not contain the Cu back contact, easier control corrosion reaction process, the stability of device performance and good reproducibility can significantly improve the performance of solar cell.
Description of drawings
Fig. 1 is the basic block diagram of CdTe solar cell.
Fig. 2 a-2e is the surface corrosion of CdTe film and the schematic diagram that is equipped with the CdTe solar cell with this legal system.
Symbolic representation among Fig. 1 and Fig. 2: G is a glass substrate, and T is a nesa coating, and W is CdS, and A is CdTe, and Te is a tellurium, and B is a back contact, and M is a back electrode.
Embodiment
Below in conjunction with accompanying drawing 2 and embodiment in detail the present invention is described in detail.
Referring to accompanying drawing 2, the CdTe film sample that adopts in the embodiment of the invention is through conventional CdCl 2Annealing in process, its structure are that (Fig. 2 a) inserts above-mentioned CdTe film sample in the aforesaid corrosive liquid glass substrate (G)/nesa coating (T)/n-CdS (W)/p-CdTe (A), oxidant HNO in corrosive liquid 3And buffer NaAc effect down, generates rich Te (Te) layer (Fig. 2 b) on p-CdTe (A) surface.In whole corrosion process, the temperature of corrosive liquid is controlled in 20 ℃～50 ℃ the scope, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid, the mixed liquor of NaAc and deionized water, wherein NaAc is 1g/L～30g/L, nitric acid, glacial acetic acid, deionized water (volume ratio) is (1～5): (60～100): (10～60), 1～15 minute time of corrosion, etching time and temperature can be determined (intensity at Te peak characterizes in the size of the square resistance that what of Te are recorded by four point probe or the X-ray diffraction) according to the Te that generates.Subsequently, use deionized water rinsing, and dry up with nitrogen.At last, deposition contains Cu or does not contain Cu back contact (B), as ZnTe:Cu or HgTe:Cu or Sb 2Te 3Or NiTe 2In any, thickness 30nm～200nm, and evaporation back electrode (M), a kind of as among Ni, Ni/Al alloy or the Au, the about 100nm of thickness～3 μ m has finished the preparation of CdTe solar cell, like this shown in Fig. 2 c.
Embodiment one:
(1) temperature of corrosive liquid is controlled under 40 ℃ the situation, sample is put into corrosive liquid, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid and deionized water mixes with 1: 100: 40 volume ratio, and the NaAc of adding is 15g/L, and etching time is 1 minute.
(2) take out sample, with deionized water rinsing for several times, dry up with nitrogen.
(3) evaporate high-purity ZnTe source (99.999%) He Tongyuan (99.999%) with the high-purity ZnTe target of sputtering method cosputtering (99.999%) and Cu target (99.999%) or vacuum coevaporation method, the about 100nm of deposit thickness, anneal～190 ℃, again deposition～200nm metal electrode Ni.
Embodiment two:
(1) temperature of corrosive liquid is controlled under 35 ℃ the situation, sample is put into corrosive liquid, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid and deionized water mixes with 1: 100: 30 volume ratio, and the NaAc of adding is 15g/L, and etching time is 2 minutes.
(2) take out sample, with deionized water rinsing for several times, dry up with nitrogen.
(3) be coated in CdTe surface after the corrosion with the 10%HgTe:Cu/90% black lead wash, nitrogen protection annealing～20 minutes, temperature～290 ℃, deposition～100nm metal electrode Au again.
Embodiment three:
(1) temperature of corrosive liquid is controlled under 30 ℃ the situation, sample is put into corrosive liquid, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid and deionized water mixes with 1.5: 100: 30 volume ratios, and the NaAc of adding is 20g/L, and etching time is 3 minutes.
(2) take out sample, with deionized water rinsing for several times, dry up with nitrogen.
(3) evaporate high-purity Sb source (99.999%) and Te source (99.999%) with the high-purity Sb target of sputtering method cosputtering (99.999%) and Te target (99.999%) or vacuum coevaporation method, deposition rate is than (0.4～0.7), the about 100nm of thickness, anneal～200 ℃, deposit Ni/Al electrode (Ni:50nm again; Al:3 μ m).
Embodiment four:
(1) temperature of corrosive liquid is controlled under 30 ℃ the situation, sample is put into corrosive liquid, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid and deionized water mixes with 1.5: 100: 30 volume ratios, and the NaAc of adding is 20g/L, and etching time is 3 minutes.
(2) take out sample, with deionized water rinsing for several times, dry up with nitrogen.
(3) with sputtering method cosputtering high-purity N i target (99.999%) and Te target (99.999%), deposition rate is than about (0.05～0.3), and the about 100nm of thickness anneals～200 ℃, again deposition～200nm metal electrode Ni.
Embodiment five:
(1) temperature of corrosive liquid liquid is controlled at 25 ℃, sample is put into corrosive liquid, corrosive liquid is that mass percent is respectively 65%～68% nitric acid, 99.5% glacial acetic acid and deionized water mixes with 1.5: 100: 30 volume ratios, and the NaAc of adding is 20g/L, and etching time is 15 fens kinds.
(2) take out sample, with deionized water rinsing for several times, dry up with nitrogen.
(3) preparation of back contact and metal electrode is with the step among the embodiment one～four (3).

Claims (5)

1. the caustic solution of a CdTe thin film solar cell is characterized in that: earlier CdTe film sample to be corroded is put into the corrosive liquid that nitric acid, glacial acetic acid, deionized water and NaAc form, temperature is controlled at 20 ℃～50 ℃, 1～15 minute time; Dry up then the CdTe film sample deionized water rinsing after the corrosion, and with nitrogen; At last, on the CdTe film sample of corrosion, deposit back contact and back electrode with preparation CdTe solar cell.
2. the caustic solution of CdTe thin film solar cell as claimed in claim 1, it is characterized in that: the mass percent 65%～68% of nitric acid in the corrosive liquid, the mass percent of glacial acetic acid is 99.5%, the volume ratio of nitric acid, glacial acetic acid, deionized water is (1～5): (60～100): (10～60), NaAc is 1g/L～30g/L.
3. the caustic solution of CdTe thin film solar cell as claimed in claim 1 is characterized in that: the structure of CdTe film sample is glass substrate/nesa coating/n-CdS/p-CdTe, and has passed through CdCl 2Annealing in process.
4. the caustic solution of CdTe thin film solar cell as claimed in claim 1 is characterized in that: back contact is ZnTe:Cu, HgTe:Cu, Sb for containing Cu or not containing the Cu material 2Te 3Or NiTe 2In any, thickness 30nm～200nm.
5. the caustic solution of CdTe thin film solar cell as claimed in claim 1 is characterized in that: back electrode is a kind of among Ni, Ni/Al alloy or the Au, thickness 100nm～3 μ m.
CNB2008100457312A 2008-08-05 2008-08-05 The caustic solution of CdTe thin film solar cell Expired - Fee Related CN100555679C (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
MY164919A (en) * 2009-09-11 2018-02-15 First Solar Inc Photovoltaic back contact
US8524524B2 (en) 2010-04-22 2013-09-03 General Electric Company Methods for forming back contact electrodes for cadmium telluride photovoltaic cells
CN101833069A (en) * 2010-05-14 2010-09-15 沈阳汉锋新能源技术有限公司 Detection device of thin film conversion rate
CN108493296A (en) * 2018-03-20 2018-09-04 暨南大学 A kind of flexible CdTe thin film solar cell and its preparation method and application
CN110021683A (en) * 2019-03-07 2019-07-16 中山瑞科新能源有限公司 A kind of cadmium telluride solar cell substrate treatment process
CN110246925B (en) * 2019-05-13 2021-03-23 中山瑞科新能源有限公司 Process for etching positive surface of cadmium telluride solar cell panel

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
硝酸-冰乙酸腐蚀对CdTe太阳电池性能的影响. 李卫等.四川大学学报，第39卷第4期. 2007
硝酸-冰乙酸腐蚀对CdTe太阳电池性能的影响. 李卫等.四川大学学报，第39卷第4期. 2007 *

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