Promising Sb 2 (S,Se) 3 Solar Cells with High Open Voltage by Application of a TiO 2 /CdS Double Buffer Layer

Sb 2 (S,Se) 3 has gathered a lot of attention recently as a promising alternative absorber material. However, the efficiencies of Sb 2 (S,Se) 3 devices are seriously restricted by the low open circuit voltage ( V oc ). In this work, Sb 2 (S,Se) 3 devices equipped with a TiO 2 /CdS double buffer layer are prepared by a hydro‐thermal method, which aims to overcome the V oc deficit. The obtained average V oc of the devices is 785 mV and the champion efficiency of 5.73% is also achieved with a highest V oc  = 792 mV, Jsc = 12.03 mA cm −2 , FF = 60.9%. The improvement of V oc is benefited from the reduced band gap offset after application of the double buffer layer. The non‐encapsulated device could keep an average power conversion efficiency of 5.69% after being stored in ambient air over a month. This indicates the great potential of a double buffer layer in new chalcogenide photovoltaic devices.