Impact of Ag doping on Cu3BiS3 solar cell performance

Ternary compound semiconductor Cu3BiS3 has been perceived as a potential candidate of solar absorber materials in recent years, due to the low–toxic and earth–abundant component elements as well as excellent optoelectronic properties. However, the fundamental properties vital for Cu3BiS3 photovoltaic device have not been fully explored and the efficiency is still at an extremely low level. Herein, a cation doping strategy was introduced during preparing Cu3BiS3 absorber layers to optimize the material properties and thereby improve the device performances. Basing on a one-step solution method, the effects of Ag doping on the structural, optical, electrical and photovoltaic behaviors of Cu3BiS3 film were investigated in detail. Our results demonstrate that appropriate Ag doping can enlarge the grain size, improve the film compactness, enhance the light absorption, broaden the band gap and increase the carrier concentration of absorber layer. As a result, the photovoltaic performance is also evidently promoted, achieving a highest efficiency improvement of ~85% relative to the undoped Cu3BiS3 solar cell device. Higher Ag incorporation, however, causes phase separation and dramatically deteriorates the absorber properties.