Towards high efficiency inverted Sb2Se3 thin film solar cells

Sb2Se3 as a rising star semiconducting material with a bandgap of 1.1 eV has played a role of the absorber in the thin film solar cells. Regular device architectures such as metal grids/buffer/Sb2Se3/metal electrode, or transparent electrode film/buffer/Sb2Se3/metal electrode have been fabricated both experimentally and theoretically and exhibit relatively good photovoltaic performances. Yet the theoretical power-conversion efficiency is not competitive with commercial thin film solar cells. Therefore, we propose an inverted architecture with top illumination through ITO substrate, with allocating the hole transport layer (HTL) on top of Sb2Se3 and stacking electron transport layer beneath the Sb2Se3. Indeed an optimal power conversion efficiency of 24.7% and fill factor of 80.3% have been simulated in the solar devices with the selected NiO as the HTL. The improvement in solar cell performances stems from the satisfying bandgap alignment and improved hole conductivity due to the high acceptor concentration of the chosen material. Further increase of the device performances depend on the high quality Sb2Se3 thin films, i.e., with negligible defects states and the suppression of defects at the Sb2Se3/HTL interfaces.