Rapid thermal processing of CuInSe2 electroplated precursors for CuIn(S,Se)2-based thin film solar cells

International audienceDuring the elaboration of standard CISEL™cells, electroplated CuInSe2 precursors undergo a rapid thermal processing (RTP) in a sulfur-containing atmosphere to promote grain growth and enable sulfurization of the precursor. The aim of this work is to show how structural and morphological properties of the CuIn(S,Se)2-based solar cells can be modified with RTP parameters, namely temperature, heating rate, and sulfur addition. X-ray diffractograms show that the preferential (112) orientation of the electrodeposited CuInSe2 precursor is maintained after annealing but the coefficient of crystallographic texture can be modified with specific RTP parameters. It is also shown that the quantity of sulfur incorporated in the chalcopyrite lattice can be controlled and reaches almost pure CuInS2 according to the sulfur quantity used during the RTP. Another effect of the RTP annealing is to form a Mo(S,Se)2 layer which can lead to a quasi-ohmic contact between the molybdenum and the absorber. The properties of the Mo(S,Se)2 buffer layer are also studied according to the process parameters and an increase of the annealing temperature or of the sulfur concentration tends to increase the thickness of this laye

State-of-the-art laser adhesion test (LASAT)

This paper proposes a state-of-the-art laser adhesion test. It consists of testing material interfaces with laser-driven shock wave. Since the first demonstration in the 1980s by Vossen, many studies and developments have been done. This paper presents recent experiments and developments on the basic physics involved. Results show the ability of the technique to perform a quantitative adhesion test for a wide range of materials and configurations. Edge effect principle and ultra-short shock wave give perspectives for new applications for multi-layer combination of material. Fundamental principles are evidenced through experiments on bulk ductile materials before demonstrating their application to coated systems

Relations traitement thermique phases adhérence dans les couches minces constituant les cellules photovoltaïques CuIn(Sx,Se1-x)2 Electrodéposées (CISEL)

Le semiconducteur CuIn(Sx,Se1-x)2 constituant les cellules photovoltaïques CISEL a fait l objet d une étude à partir de deux précurseurs électrodéposés. L un est un semi-conducteur CuInSe2 nanocristallisé, l autre est un alliage métallique cuivre-indium. Recuits en présence de soufre, ces deux précurseurs conduisent à deux absorbeurs chalcopyrites, le premier CuIn(Sx,Se1-x)2 est riche en soufre alors que le deuxième CuInS2 est dépourvu de sélénium. Lors de la formation du CuIn(Sx,Se1-x)2, la croissance des grains de CuInSe2 est concomittante avec la substitution du sélénium par le soufre. Pour le CuInS2 l oxydation du cuivre et de l indium par le soufre produit des phases soufrées qui réagissent pour former la chalcopyrite. La comparaison des relations entre traitement thermique, formation des phases et adhérence pour les deux chemins réactionnels a permis d optimiser le recuit et de comprendre pourquoi l adhérence du CuIn(Sx,Se1-x)2 au substrat est supérieure à celle du CuInS2. Le modèle de comportement mécanique proposé pour le multicouche explique à la fois les ruptures mécaniques ainsi que les phénomènes de croissance sous contrainte observés. Afin d améliorer l étude de l adhérence des multicouches photovoltaïques, on a montré que la technique LASAT® pouvait être utilisée de manière innovante avec des lasers femtosecondes pour mesurer l adhérence de couches submicrométriques constituant le multicouche photovoltaïque.PARIS-MINES ParisTech (751062310) / SudocSudocFranceF

Doping profile measurement on textured silicon surface

In crystalline silicon solar cells, the front surface is textured in order to lower the reflection of the incident light and increase the efficiency of the cell. This texturing whose dimensions are a few micrometers wide and high, often makes it difficult to determine the doping profile measurement. We have measured by secondary ion mass spectrometry (SIMS) and electrochemical capacitance voltage profiling the doping profile of implanted phosphorus in alkaline textured and in polished monocrystalline silicon wafers. The paper shows that SIMS gives accurate results provided the primary ion impact angle is small enough. Moreover, the comparison between these two techniques gives an estimation of the concentration of electrically inactive phosphorus atoms

Doping profile measurement on textured silicon surface

In crystalline silicon solar cells, the front surface is textured in order to lower the reflection of the incident light and increase the efficiency of the cell. This texturing whose dimensions are a few micrometers wide and high, often makes it difficult to determine the doping profile measurement. We have measured by secondary ion mass spectrometry (SIMS) and electrochemical capacitance voltage profiling the doping profile of implanted phosphorus in alkaline textured and in polished monocrystalline silicon wafers. The paper shows that SIMS gives accurate results provided the primary ion impact angle is small enough. Moreover, the comparison between these two techniques gives an estimation of the concentration of electrically inactive phosphorus atoms

Sulfurization of Cu-In electrodeposited precursors for CuInS2-based solar cells

International audienceCu-In electrodeposited layers were annealed using rapid thermal processing (RTP) in a reactive atmosphere containing sulfur vapors. The CuInS2 formation mechanism during sulfurization of electrodeposited precursors proceeds mainly through direct sulfurization of the metallic Cu-In alloy, forming spinel CuIn5S8 and chalcopyrite CuInS2 ternary phases. During the heating step, the Cu-In metallic alloy gets richer in copper as the temperature increases and transforms from CuIn2 to Cu11In9, then Cu16In9 and finally to Cu7In3. The use of rapidly cooled samples stopped after different durations of the process along with ex-situ XRD analysis enabled us to differentiate the Cu16In9 and Cu7In3 phases. Finally, the efficiency of the solar cells made with the two-step electrodeposition and RTP low-cost process reaches 11% (active area 0.421 cm2), which is close to the results obtained for cells made with PVD precursors

Prediction of Photovoltaic Cu(In,Ga)Se2 p-n Device Performance by forward Bias Electrochemical Analysis of Only the p-Type Cu(In,Ga)Se2 Films

This work is an attempt to rate the quality of Mo/Cu(In,Ga)Se2 films intended for fabrication of photovoltaic devices. The procedure is based on the simple current-voltage electrochemical analysis of the bilayer in a Eu2+/3+-containing electrolyte solution. Two series of bilayer samples were tested electrochemically, while sister samples were completed into Mo/Cu(In,Ga)Se2/CdS/i-ZnO/Al:ZnO/Ni-Al solid state devices and their current-voltage characteristics measured in the dark. A correlation was found between the reverse saturation current density of the solid state devices and an analogous parameter extracted from the electrochemical response in forward bias. While Eu2+ was found to be metastable in water posing restrictions to the application, reproducible measurements were achieved with a methanol-based solution. The intrinsic simplicity of the proposed methodology makes it particularly suitable for the implementation of a low-cost diagnostic tool

Laser shock adhesion test (LASAT) of thin films in CuInS2-based solar cells

International audienc

Development of low-carbon footprint process for passivating contacts on p-type silicon wafers

International audienc

Impact of PECVD μc-Si:H deposition on tunnel oxide for passivating contacts

Passivating contacts are becoming a mainstream option in current photovoltaic industry due to their ability to provide an outstanding surface passivation along with a good conductivity for carrier collection. However, their integration usually requires long annealing steps which are not desirable in industry. In this work we study PECVD as a way to carry out all deposition steps: silicon oxide (SiOx), doped polycrystalline silicon (poly-Si) and silicon nitride (SiNx:H), followed by a single firing step. Blistering of the poly-Si layer has been avoided by depositing (p+) microcrystalline silicon (μc-Si:H). We report on the impact of this deposition step on the SiOx layer deposited by PECVD, and on the passivation properties by comparing PECVD and wet-chemical oxide in this hole-selective passivating contact stack. We have reached iVoc > 690 mV on p-type FZ wafers for wet-chemical SiOx\(p+) μc-Si\SiNx:H with no annealing step