Back contact interfacial modification mechanism in highly-efficient antimony selenide thin-film solar cells

Antimony selenide (Sb2Se3) is a potential photovoltaic (PV) material for next-generation solar cells and has achieved great development in the last several years. The properties of Sb2Se3 absorber and back contact influence the PV performances of Sb2Se3 solar cells. Hence, optimization of back contact characteristics and absorber orientation are crucial steps in raising the power conversion efficiency (PCE) of Sb2Se3 solar cells. In this work, MoO2 was introduced as an intermediate layer (IL) in Sb2Se3 solar cells, and comparative investigations were conducted. The growth of (211)-oriented Sb2Se3 with large grains was facilitated by introducing the MoO2 IL with suitable thickness. The MoO2 IL substantially lowered the back contact barrier and prevented the formation of voids at the back contact, which reduced the thickness of the MoSe2 interface layer, inhibited carrier recombination, and minimized bulk and interfacial defects in devices. Subsequently, significant optimization enhanced the open-circuit voltage (VOC) of solar cells from 0.481 V to 0.487 V, short-circuit current density (JSC) from 23.81 mA/cm2 to 29.29 mA/cm2, and fill factor from 50.28% to 57.10%, which boosted the PCE from 5.75% to 8.14%.