Double layer CuInS_2 absorber using spray pyrolysis: A better candidate for CuInS_2/In_2S_3 thin film solar cells

摘要

In the fabrication of CuInS_2/In_2S_3 solar cell using chemical spray pyrolysis (CSP) deposition technique, one of the major problems is the diffusion of Cu towards the In_2S_3 layer affecting stability and repeatability of the CuInS_2/In_2S_3 cells. In order to ensure a Cu-free In_2S_3 layer, a 'double layer structure' of CuInS_2 film, having a Cu-rich first layer and In-rich second layer was deposited using manual CSP technique. In this paper, we present the difference in material properties of single and double layered CuInS_2 films and the results of characterisation of the junctions prepared using such films with β-In_2S_3 films. Better crystallinity as well as larger and densely packed grains were observed for the CuInS_2 films having 'double layer structure'. Such samples also possessed two band gaps, which was not due to the presence of different phases, but due to the Cu-rich and Cu-poor layers. In addition, their low resistivity makes the double layered CuInS_2 film more beneficial for photovoltaic applications.