Enhanced Performance of the Sb₂Se₃ Thin-Film Solar Cell by Organic Molecule-Induced Crystallization and Suppression of the Interface Recombination

Antimony selenide (Sb2Se3) is an emerging photovoltaic material. We demonstrate that an organic small molecule of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) can induce the crystallization of the Sb2Se3 film during the annealing treatment. By introducing an NPB buffer layer, the Sb2Se3 film crystal quality is improved, and the photogenerated carrier lifetime is increased. In addition, the introduction of an NPB layer can suppress the interface recombination near the anode. The solar cell was fabricated using C60 as an electron transport layer by vacuum thermal evaporation. We took indium tin oxide/NPB (6.0 nm)/Sb2Se3 (∼50 nm)/C60 (5.0 nm)/Alq3 (3.0 nm)/Al as the device architecture, where Alq3 is tris(8-hydroxyquinolinato) aluminum. By adding an NPB buffer layer, the open-circuit voltage is elevated from 0.35 to 0.40 V, and the power conversion efficiency is dramatically enhanced from 3.21 to 5.03%. We attributed the improved performance to the suppression of the bulk and the interface recombination.