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RESEARCH PRODUCT

Partial cation-substitution in the sulphide kesterite: Absorber and heterojunction engineering

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International audience; The kesterite-based solar cells still suffer from a low conversion efficiency due to the large defect of the open circuit voltage Voc. This defect is mainly due to several problems related to the absorber material and the device interfaces. It has been reported that the partial cation substitution in the kesterite structure, can improve many properties of the absorbent layer and the device, i.e. improve the grain size, minimise the anti-site defects and disorder in the Cu-Zn plane, ameliorate the charge separation at the buffer/absorber interface. In this work, thin films of suphide kesterite are made by substituting copper (Cu) with silver (Ag) and zinc with manganese (Mn) or cadmium (Cd). Different concentrations have been applied to explain the influence of the chemical composition on the properties. The films were layered on glass substrate from colloidal solution by spin coating technique followed by heat treatment under sulphide. The p-n junctions were made by chemical bath (CBD) deposition of CdS on the kesterite thin films. An in-depth study by XPS has been applied to determine the band alignment through the heterojunctions. By this work, we have been able to evaluate experimentally the electronic properties of the Kesterite alloy with different cations and to validate this strategy to reduce the heterointerfaces recombination.