Characterisation of ultrasonically sprayed InxSy buffer layers for Cu(In,Ga)Se2 solar cells

In order to replace chemical bath deposited (CBD) CdS buffer layers in Cu(In,Ga)Se2 (CIGS) solar cells by an alternative material, InxSy thin-film buffer layers were prepared by ultrasonic spray pyrolysis at various substrate temperatures. X-ray Diffraction measurements confirmed that the films contained primarily the tetragonal In2S3 phase. X-ray Photoelectron Spectroscopy measurements revealed a small concentration of chlorine impurity throughout the InxSy layer. By depositing the indium sulphide layer as buffer layer in the CIGS solar cell configuration, a maximum solar cell efficiency of 8.9% was achieved, whilst the reference cell with CdS/CIGS on a similar absorber exhibited 12.7% efficiency. Additionally, light soaking enhanced the efficiency of InxSy/CIGS cells primarily by improvements in fill factor and open circuit voltage.