Double layer CuInS2 absorber using spray pyrolysis: A better candidate for CuInS2/In2S3 thin film solar cells

In the fabrication of CuInS2/In2S3 solar cell using chemical spray pyrolysis (CSP) deposition technique, one of the major problems is the diffusion of Cu towards the In2S3 layer affecting stability and repeatability of the CuInS2/In2S3 cells. In order to ensure a Cu-free In2S3 layer, a ‘double layer structure’ of CuInS2 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 CuInS2 films and the results of characterisation of the junctions prepared using such films with β-In2S3 films. Better crystallinity as well as larger and densely packed grains were observed for the CuInS2 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 CuInS2 film more beneficial for photovoltaic applications.

► We present double layer CuInS2 as a better absorber layer.
► Double layer CuInS2 helps to prevent Cu diffusion in CuInS2/In2S3 cell.
► Cu:In:S ratio of CuInS2 film determines the opto-electronic properties.
► Lowest resistivity for double layer structure of CuInS2.
► CuInS2 with Cu rich first layer and Cu poor second layer will be very advantageous.