Internal homojunction Sb2Se3 solar cell

Antimony selenide (Sb 2 Se 3 ) has emerged as a promising thin-film photovoltaic absorber due to its ideal bandgap (1.1–1.3 eV), high absorption coefficient (>10 5  cm −1 ) and environmentally benign composition. However, Sb 2 Se 3 solar cells (SSCs) often suffer from large open-circuit voltage losses owing to the weak built-in fields and severe non-radiative recombination at the interfaces and within the absorber layer. Here we demonstrate a composition-driven strategy for controlling carrier polarity that we used to form an n-type/p-type homojunction within the Sb 2 Se 3 absorber layer. By precisely tuning the chemical potentials of Se and Sb, we are able to manipulate the conductivity type and achieve carrier densities exceeding 10 14  cm −3 for the n- and p-type states. With this materials design, we demonstrate that incorporating the p–n homojunction into a planar SSC simultaneously enhances the built-in electric field and passivates deep-level defects. These synergistic effects promote carrier separation, reduce non-radiative recombination and accelerate carrier extraction. As a result, the internal-homojunction-enhanced SSC delivers a power conversion efficiency of 10.15% for thermally evaporated Sb 2 Se 3 devices and an ultralow open-circuit voltage deficit of 0.459 V. This study proposes a proof-of-concept device structure for SSCs that opens a new pathway for improving device efficiency.