Reactively sputtered CdS:O buffer layers for substrate Sb2Se3 solar cells

Antimony selenide (Sb2Se3) is an emerging and promising photovoltaic material. High controllability for the energy level of buffer layers is greatly desirable for achieving higher performance Sb2Se3 solar cells due to the formation of heterojunction at the buffer/Sb2Se3 absorber interface. In this work, the CdS:O buffers were prepared by using a reactive sputtering technique including an Ar/O2 mixture gas and a CdS ceramic target, and a composite buffer were fabricated with a structure of CBD-CdS (∼10 nm)/CdS:O. The interface damage induced by sputtering is investigated, and untra-thin CBD-CdS is performed to recover the plasma induced damage at the CdS:O/Sb2Se3 heterojunction interface. By optimizing the S/(S+O) composition ratio and the phase component of the composite buffer, wide band-gap buffer layers were achieved, and the device spectra response and device parameters JSC and VOC were improved. It was found that the composite CdS:O buffer optimizes the heterojunction interface band alignment and further efficiently reduce the interface recombination, enhanced the transfer and collection of photogenerated carriers.