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Black Silicon Obtained in Two-Step Short Wet Etching as a Texture for Silicon Solar Cells - Surface Microstructure and Optical Properties Studies

Kulesza-Matlak G., Gawlińska K., Starowicz Z., Sypień A., Drabczyk K., Drabczyk B., Lipiński M., Zięba P.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 2

1009--1017

EN

In this study a two-step short wet etching was implemented for the black silicon formation. The proposed structure consists of two steps. The first step: wet acidic etched pits-like morphology with a quite new solution of lowering the texturization temperature and second step: wires structure obtained by a metal assisted etching (MAE). The temperature of the process was chosen due to surface development control and surface defects limitation during texturing process. This allowed to maintain better minority carrier lifetime compared to etching in ambient temperature. On the top of the acidic texture the wires were formed with optimized height of 350 nm. The effective reflectance of presented black silicon structure in the wavelength range of 300-1100 nm was equal to 3.65%.

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Time efficient texturization of multicrystalline silicon in the HF/HNO3 solutions and its effect on optoelectronic parameters of solar cells

Kulesza G., Panek P., Zięba P.

Archives of Civil and Mechanical Engineering

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2014

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Vol. 14, no. 4

595--601

EN

In this paper the improving photovoltaic conversion efficiency of multicrystalline silicon solar cells obtained by acid texturization is presented. Different solutions from two various composition ranges of HF:HNO3:CH3COOH/H2O system were examined. The influence of the HF/HNO3 content, type of diluents and texturization process time on the basic optoelectronic parameters of multicrystalline solar cells was also studied. This research brings new experimental receipt which allows to obtain the proper surface morphology after the texturization in a very short time of 60 s. The optimal acid volume etching ratio was found to be HF:HNO3:H2O = 7:1:2. For the first time, etching lasting 1 min causes the lowering the reflectivity value below 12% and also improves the conversion efficiency by 22% in relation to the reference sample without acid texture. The inverse HF/HNO3 ratio resulted in two times higher diameter of obtained rounded pits which allowed better coverage of the front metal grid patterning over the flat surface. Moreover, the higher reflectance value was accompanied by relatively high efficiency up to 13.9%.

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Silicon solar cells efficiency improvement by the wet chemical texturization in the HF/HNO3/diluent solution

Kulesza G., Panek P., Zięba P.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 1

291-295

EN

The paper presents the results of the texturization process of the multicrystalline silicon wafers carried out in ternary HF/HNO3/diluent solution, where the diluent was either CH3COOH or H2O, at varying HF/HNO3 volume ratio and different time of texturization process. The technique of scanning electron microscopy was used to characterize the morphology of the obtained multicrystalline silicon surfaces, with subsequent surface reflectivity measurements. The appropriate selection of mixture components lead to a significant reduction in the reflectivity of the incident solar radiation in the relatively short time of 60 seconds. The resultant electric parameters were nearly the same as those for the commercial samples but obtained after 3 minutes.

PL

Autorzy zaprezentowali wyniki badań dotyczących procesu teksturyzacji w roztworze HF/HNO3/rozpuszczalnik stosowanego dla płytek krzemu multikrystalicznego, gdzie jako rozpuszczalnik stosowano zamiennie CH3COOH oraz H2O. W badaniach jako zmienne przyjęto objętościowy stosunek HF/HNO3 oraz czas procesu. Morfologia powierzchni uzyskana po chemicznej modyfikacji krzemu została scharakteryzowana przy użyciu skaningowej mikroskopii elektronowej, a następnie zbadano wpływ takiego ukształtowania powierzchni na odbicie promieniowania słonecznego. Autorzy wykazali, że odpowiednie dobranie składu mieszaniny trawiącej pozwala na uzyskanie najniższych wartości odbicia w stosunkowo krótkim czasie 60 sekund. Ponadto parametry elektryczne zmodyfikowanych ogniw słonecznych nie odbiegały od tych uzyskanych komercyjnie w czasie trzykrotnie dłuższym.

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Zanieczyszczenia multikrystalicznego krzemu modyfikowanego procesem geterowania

Piotrowski T., Kruszewski P., Lipiński M.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 4

17-20

PL

W pracy określono zawartość żelaza międzywęzłowego (Fe i) w mc-Si po procesie geterowania fosforem oraz ujawniono występowanie akceptorowego poziomu rekombinacyjnego o energii aktywacji Ev = +0,338 eV stosując pomiary Laplace DLTS.

EN

The interstitial iron (Fe i ) content in multicrystalline silicon (mc-Si) after phosphorous gettering was determined and acceptor recombination level with activation energy Ev = +0.338 eV was detected by Laplace DLTS measurements.

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Wyznaczanie czasu życia nośników ładunku w płytkach krzemowych z pomiaru absorpcji na nośnikach swobodnych

Piotrowski T., Kasjaniuk S.

Elektronika : konstrukcje, technologie, zastosowania

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2010

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Vol. 51, nr 9

100-102

PL

Przedstawiono metodykę określania czasu życia nośników ładunku, wykorzystującą pomiar absorpcji optycznej nośników swobodnych w podczerwieni, pozwalającą na szybki, bezdotykowy i przeprowadzany z dużą rozdzielczością przestrzenną pomiar tego głównego parametru rekombinacyjnego. Metodyka ta uzupełnia dotychczas stosowane bezdotykowe metody pomiarowe czasu życia nośników ładunku stosowane w diagnostyce przemysłowej a może znaleźć szczególne zastosowanie do charakteryzacji multikrystalicznego krzemu.

EN

A method of charge carrier lifetime determination by using free carriers absorption measurement is presented. The method is quick, contactless and has good spatial resolution. It complements known contactless lifetime measurement methods applied in industry diagnostics and can be especially useful for multicrystalline silicon characterization.

6

Pomiary czasu życia nadmiarowych nośników ładunku w obszarach bliskich granicom ziaren z wykorzystaniem barierowego efektu fotowoltaicznego

Piotrowski T., Sikorski S., Kasjaniuk S., Lipiński M.

Elektronika : konstrukcje, technologie, zastosowania

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2010

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Vol. 51, nr 5

74-76

PL

W pracy przedstawiono sposób określania efektywnego czasu życia nadmiarowych nośników prądu w obszarach granic ziaren krzemowych płytek multikrystalicznych przeznaczonych do wytwarzania ogniw słonecznych. Do pomiaru wykorzystano efekt fotowoltaiczny powstający na barierze potencjału związanej z granicą ziaren. Pomiary weryfikowano standardową metodą pomiaru zaniku fotoprzewodnictwa w czasie z detekcją mikrofalową.

EN

A method of effective carrier lifetime determination near grain boundaries in multicrystalline silicon wafers for solar cells is presented. Photovoltaic effect on potential barrier at grain boundary is used for measurements. Obtained results are werified by method of photoconductivity decay with microwave beam detection.

7

Development of the laser method of multicrystalline silicion surface texturization

Dobrzański L., Drygała A., Panek P., Lipiński M., Zięba P.

Archives of Materials Science and Engineering

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2009

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Vol. 38, nr 1

5-11

EN

Purpose: The aim of the paper is to demonstrate a laser method of multicrystalline silicon texturization. This means creating a roughened surface so that incident light may have a larger probability of being adsorbed into the solar cell. It was demonstrated, that laser processing is very promising technique for texturing multicrystalline silicon independent on crystallographic orientation of grains compared to conventional texturing methods. Design/methodology/approach: The topography of laser textured surfaces were investigated using ZEISS SUPRA 25 scanning electron microscope and LSM 5 Pascal ZEISS confocal laser scanning microscope. The reflectance of produced textures was measured by Perkin-Elmer Lambda spectrophotometer with an integrating sphere. Electrical parameters of manufactured solar cells were characterized by measurements of I-V illuminated characteristics under standard AM 1.5 radiation. Findings: The texturing of multicrystalline silicon surface using Nd:YAG laser makes it possible to increase absorption of the incident solar radiation. Laser processing is a promising method for texturization of multicrystalline silicon compared to conventional texturing methods applied in used technology of solar cells. Research limitations/implications: Laser processing introduce into the bulk of material some unwanted effects, having detrimental influence on the main parameters of processed silicon wafers. Solar cells manufactured from laser-textured multicrystalline silicon wafers demonstrate worse electrical performance than cells manufactured from the non-textured wafers after saw damage removal as well as wafers textured by etching in alkaline solutions. Chemical etching by means of potassium alkali made it possible to increase cell efficiency. Originality/value: Laser texturing has been shown to have great potential as far as its implementatnion into industrial manufacturing process of solar cell is concerned.

8

Surface texturing of multicrystalline silicon solar cells

Dobrzański L. A., Drygała A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 1

77-82

EN

Purpose: The aim of the paper is to elaborate a laser method of texturization multicrystalline silicon. The main reason for taking up the research is that most conventional methods used for texturization of monocrystalline silicon are ineffective when applied for texturing multicrystalline silicon. This is related to random distribution of grains of different crystalographic orientations on the surface of multicrystalline silicon. Design/methodology/approach: The topography of laser textured surfaces were investigated using ZEISS SUPRA 25 and PHILIPS XL 30 scanning electron microscopes and LSM 5 Pascal ZEISS confocal laser scanning microscope. The reflectance of produced textures was measured by Perkin-Elmer Lambda spectrophotometer with an integrating sphere. Electrical parameters of manufactured solar cells were characterized by measurements of I-V illuminated characteristics under standard AM 1.5 radiation. Findings: A method of texturing of multicrystalline silicon surface using Nd:YAG laser appeared to be much more independent on grains crystallographic orientation compared to conventional texturing methods. Laser texturing makes it possible to increase absorption of the incident solar radiation. Research limitations/implications: The major inconveniences are surface damage in the heat affected zone and depositing of foreign materials during laser treatment. Applied etching procedure allows for obtaining solar cells of high efficiency larger in relation to cells without texture. Originality/value: This paper demonstrates that laser texturing has been shown to have great potential as far as its implementation into industrial manufacturing process of solar cells is concerned.

9

Effect of dislocation density on the efficiency of multicrystalline silicon solar cells

Benmohamed Z., Remram M.

Materials Science Poland

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2007

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Vol. 25, No. 1

243--249

EN

The behaviour of structural defects is still one of the major problems in multicrystalline silicon. The properties of solar cells made from these materials are mainly determined by dislocations, grain boundaries and intragrain defect impurities such as oxygen and carbon. Interactions between dislocations and impurities are also an important factor influencing the minority carrier diffusion length and then multicrystalline solar cells performances. In this paper, the effect of dislocations on minority carrier diffusion length is analysed and discussed. We carried out the calculation on the cell efficiency of multicrystalline silicon solar cell obtained from wafers cut put of ingots grown by Polix of Photowatt and Sitix of Sumitomo. A comparison between solar cells efficiency for the two materials outlined above is presented. Performances of the cells are estimated according to the last technological processes developed. The analyses have also been carried out to optimize solar cell performances by combining the effect of a double antireflection coating and back surface field.

10

Structure of laser treated multicrystalline silicon wafers

Dobrzański L. A., Drygała A., Konieczny J., Lelątko J.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 21, nr 2

69-72

EN

Purpose: The aim of the paper is to demonstrate influence of laser processing on multicrystalline silicon. This process is applied for texturization of solar cells. Design/methodology/approach: Evaluation of results was performed by transmission electron microscope (TEM). Findings: Performed experiments revealed that laser processing may introduce linear defects in crystallographic structure of silicon. Additionally, it was found that this kind of processing produces thin amorphous layer. Research limitations/implications: Laser scribing introduces defects. It is important to characterize their influence on the electrical properties of silicon solar cells. It is possible to remove these defects by means of chemical etching. Practical implications: The research presented in the paper was carried out to incorporate elaborated method into manufacturing process of solar cells of reduced reflectance from the front surface. Success of research is expected to lead to higher efficiency solar cells. Originality/value: value of the paper lies in finding attractive method for efficient texturization of multicrystalline silicon.

11

Application of laser in multicrystalline silicon surface processing

Dobrzański L. A., Drygała A., Panek P., Lipiński M., Zięba P.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

179-182

EN

Purpose: Surface texturisation is a common technological process in solar cell manufacturing aiming at a reduction of the light reflection losses. The standard alkaline texturing of multicrystalline silicon for solar cells is not effective because of random orientation of the grains. In this paper a method of laser texturisation has been proposed to overcome these difficulties. Design/methodology/approach: The microstructure of laser textured surface was investigated by DSM 940 OPTON scanning electron microscope (SEM). Electrical parameters of produced solar cells were characterized by measurements of I-V light characteristics under standard AM 1,5 radiation. Findings: The analysis performed in the paper revealed the existence of laser-damaged layer on the textured surface which has to be removed prior to successive technological steps to obtain solar cells of satisfactory performance. Research limitations/implications: It is suggested that future work should be done to develop a better post-scribe etching technique to remove the laser damaged layer. Originality/value: It seems to be very promising method since it can be applicable in industry.

12

Industrial technology of multicrystalline silicon solar cells

Panek P., Lipiński M., Beltowska-Lehman E., Drabczyk K., Ciach R.

Opto-Electronics Review

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2003

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Vol. 11, No. 4

269-275

EN

This paper presents current technology used to produce 100 cm² multicrystalline silicon solar cells of efficiency above 13% which was one of the main goals of the National Photovoltaic Project undertaken in the Institute of Metallurgy and Materials Science (IMMS). The general concept of the technology consists of maximum seven steps. The process sequence is based on diffusion from POCl₃ and screen printed contacts fired through a PECVD Six Ny or TiOx antireftlection coating (ARC). Co-metallisation annealing was performed in an IR furnace. The multicrystalline wafers are described using four-point probe, scanning electron microscopy (SEM), secondary ion mass spectrometer, and spectrophotometer with an integrating sphere. The completed solar cells are characterized with internal spectral response and a current-voltage characteristic. All aspects palying a role in a suitable manufacturing process are discussed. At present, multicrystalline silicon solar cells capture around a 45% share of the world photovoltaics market with a total of 540 MW being produced in 2002. Taking into account the decreasing cost of multicrystalline substrates, this relation will rise systematically.