Buffer layers and transparent conducting oxides for chalcopyrite Cu(In,Ga)(S,Se)2 based thin film photovoltaic: present status and current developments

Progress in Photovoltaics Research and Applications (Impact Factor: 9.7). 09/2010; 18(6):411–433. DOI: 10.1002/pip.955
Source: OAI

ABSTRACT The aim of the present contribution is to give a review on the recent work concerning Cd-free buffer and window layers in chalcopyrite solar cells using various deposition techniques as well as on their adaptation to chalcopyrite-type absorbers such as Cu(In,Ga)Se2, CuInS2, or Cu(In,Ga)(S,Se)2. The corresponding solar-cell performances, the expected technological problems, and current attempts for their commercialization will be discussed. The most important deposition techniques developed in this paper are chemical bath deposition, atomic layer deposition, ILGAR deposition, evaporation, and spray deposition. These deposition methods were employed essentially for buffers based on the following three materials: In2S3, ZnS, Zn1 − xMgxO.


Available from: Ahmed Ennaoui, Apr 28, 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: In2S3 thin layers can be prepared by Spray-ILGAR® (Ion Layer Gas Reaction) from indium trichloride or from indium triacetylacetonate solutions. In the first case, the film contains a controllable amount of Cl. The concentration of H2O or Cl was varied systematically in the precursor solutions that were used for the deposition of In2S3 buffer layers on commercially available Cu(Ga,In)(S,Se)2 absorbers. The layers were characterized by ultraviolet photo electron spectroscopy, optical spectroscopy, modulated surface photovoltage spectroscopy and X-ray photoelectron spectroscopy, combined with a sequential etching procedure. The latter allowed to estimate an element-specific depth profile. Experimental findings were correlated with the performance of the corresponding solar cells. The presence of H2O or Cl in the precursor solutions has a strong influence on the diffusion of Cu+ and Na+ cations from the absorber into the buffer layer. The open circuit voltage of solar cells with In2S3 buffer layers prepared from Cl-free, H2O-containing precursor solutions was higher by up to 100 mV than those from Cl-containing, but H2O-free solutions. For this reason, the average solar energy conversion efficiency of cells of the first buffer type was higher (14.7%) than for solar cells of the second type (12.1%).
    Solar Energy Materials and Solar Cells 01/2015; 132:303–310. DOI:10.1016/j.solmat.2014.08.044 · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, the effect of humidity on the growth characteristics and properties of chemical bath-deposited ZnS thin films was systematically investigated. All deposition was conducted by an open CBD system under various relative humidity levels (RH) or by a hermetic CBD system as a comparison. It shows, for films deposited by an open system, the ambient humidity plays an important role in the quality of the resultant films. Damp environments lead to powdery films. Generally, all films prepared in this study using NH3 and hydrazine hydrate as the complexing agents were amorphous or poorly crystalline. For an open system, the [H+] from the dissolved carbon dioxide in the air competes with the ammonium ions in the bath solution. According to Le Chatelier's principle, more ammonia was consumed, which favors the free [Zn+2] in the solution, facilitating the homogeneous precipitation of Zn(OH)(2) and giving rise to a powdery film. The x-ray photoelectron spectrum shows, for an open system, the content of Zn-O compounds in the form of Zn(OH)(2) and ZnO, etc., is increased by the relative humidity of the environment. The visible transmittance is reduced by RH. The higher optical band gap of the as-deposited films could be attributed to the quantum confinement effects due to the small grain size of the polycrystalline ZnS films over the substrates. (c) 2014 Elsevier B.V. All rights reserved.
    Applied Surface Science 07/2014; 307:724-730. DOI:10.1016/j.apsusc.2014.04.111 · 2.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Energy band alignment plays an important role in thin film solar cells. This article presents an overview of the energy band alignment in chalcogenide thin film solar cells with a particular focus on the commercially available material systems CdTe and Cu(In,Ga)Se2. Experimental results from two decades of photoelectron spectroscopy experiments are compared with density functional theory calculations taken from literature. It is found that the experimentally determined energy band alignment is in good agreement with theoretical predictions for many interfaces. These alignments, in particular the theoretically predicted alignments, can therefore be considered as the intrinsic or natural alignments for a given material combination. The good agreement between experiment and theory enables a detailed discussion of the interfacial composition of Cu(In,Ga)Se2/CdS interfaces in terms of the contribution of ordered vacancy compounds to the alignment of the energy bands. It is furthermore shown that the most important interfaces in chalcogenide thin film solar cells, those between Cu(In,Ga)Se2 and CdS and between CdS and CdTe are quite insensitive to the processing of the layers.
    Journal of Physics Condensed Matter 03/2015; 27(13):134201. DOI:10.1088/0953-8984/27/13/134201 · 2.22 Impact Factor