CIS thin film solar cells with evaporated InSe buffer layers

This paper describes the investigations of CIS-based solar cells with a new In_xSe_y (IS) buffer layer. Studies were concentrated on determining the deposition conditions to get In_xSe_y thin films with adequate properties to be used in substitution of the CdS buffer layer, usually employed in the fabrication of this type of devices. Before the solar cell fabrication, the buffer layers grown by evaporation of the In₂Se₃ compound were characterized through transmittance and X-ray diffraction measurements. It was found that good results can be obtained using indium selenide film as the buffer layer, grown in the In₂Se₃ phase.Solar cells with structure Mo/CIS/In₂Se₃/ZnO were fabricated. The ZnO layer was deposited by reactive evaporation and the absorber CIS layer was grown on Mo by a two-stage process. The preliminary results obtained with this type of solar cells are J_sc=30.8 mA/cm², V_oc=0.445 V, FF≈0.6 and η=8.3% with an irradiance of 100 mW/cm². Solar cells fabricated using a CdS buffer layer deposited by CBD on CIS substrate, prepared under the same conditions used in the fabrication of Mo/CIS/In₂Se₃/ZnO cells, gave the following results: V_oc=0.43 V, J_sc=34 mA/cm², FF≈0.63 and η=9.2%.