A novel cadmium free buffer layer for Cu(In,Ga)Se-2 based solar cells

Solar cells based on Cu(In,Ga)Se, were prepared replacing the ''standard buffer layer'' CdS with a In-x(OH,S)(y) thin film. The film is deposited in a chemical bath (CBD) process using an aqueous solution containing InCl3 and thioacetamide. X-ray photoemission spectroscopy measurements were performed in order to characterize the growth kinetics and the chemical composition. The influence of different concentrations of InCl3 and thioacetamide in the solution on the electrical properties of the solar cells was studied by measuring the j-V characteristics and the spectral quantum efficiencies. Capacitance-voltage (C-V) measurements indicate that the high V-alpha values of devices with the novel buffer layer are correlated with narrower space charge widths and higher effective carrier concentrations in the absorber materials. The achieved conversion efficiency of 15.7% (active area) using the cadmium free In-x(OH,S)(y) buffer demonstrates the potential of this process as an alternative to the standard chemical bath deposition of CdS.