Interface Engineering for High-Efficiency Solution-Processed Cu(In,Ga)(S,Se)₂ Solar Cells via a Novel Indium-Doped...

Indium doping of cadmium sulfide (CdS) by chemical bath deposition (CBD) can be an efficient strategy to boost the CIGSSe efficiency. However, limited by the extremely low solubility of In₂S₃, it is difficult to increase the In doping contents and inhibit the band energy-level regulation for CdS through the traditional CBD process. In this work, we perform a novel CBD method to prepare an indium-doped CdS (In:CdS) buffer, in which the indium source is sequentially slowly added in the growing aqueous solution. In this process, the In ion concentration involved in the real-time deposition is significantly reduced. Thus, compact and uniform In:CdS with higher indium doping content is obtained. Indium doping can elevate the CdS conduction band edge and construct a more favorable spike band alignment with a CIGSSe absorber. Moreover, it introduces efficient carrier transport and reduced interface defect density. As a result, improved CIGSSe heterojunction quality is realized by utilizing In:CdS. Also, the solution-processed CIGSSe device with In:CdS as a buffer yields a high efficiency of 16.4%, with a high V_OC of 670 mV and an FF of 75.3%.