CD-free Cu(In,Ga)Se2 thin-film solar modules with In2S3 buffer layer by ALCVD

The atomic layer chemical vapour deposition (ALCVD) technique allows the deposition of highly homogeneous thin-films with an excellent step coverage. This method has already shown promising results for the deposition of cadmium-free buffer layers in Cu(In,Ga)Se-2 (CIGS) thin-film solar cells (13.5% efficiency with indium sulphide buffer). In this work, the process has been up-scaled to module areas of up to 30 X 30 cm. The indium sulphide buffer layer was deposited at substrate temperatures between 160 and 220 degreesC using indium acetylacetonate and hydrogen sulphide precursors. An efficiency of eta = 10.8% (open-circuit voltage, V-OC = 592 mV; fill factor, FF = 62%; current density, j(SC) = 29.5 mA/cm(2)) for a module area of 30 X 30 cm(2) has been achieved. For laboratory cells even an efficiency of 14.9% was realised. Damp heat stability testing of CIGS mini-modules indicates a similar behaviour of both devices with ALCVD indium sulphide and solution grown cadmium-sulphide buffer layer. (C) 2003 Elsevier Science B.V. All rights reserved.