Crystal reconstruction and defect healing enabled high-quality Sb₂Se₃ films for solar cell applications

Sb2Se3 is a kind of quasi-one-dimensional solar cell absorber material, the crystal orientation and deep-level defects sensitively affect the energy conversion in Sb2Se3 solar cells. Conventionally, the development of the film synthesis method to control the crystallinity as well as the defects has been well studied, while the current methods show limited capability in tuning the critical parameters. Here, we develop a novel post-sulfurization method to manipulate the crystallization of Sb2Se3 films, which yields excellent grain structures and provides effective defect passivation. This method treats the thermal evaporation deposited Sb2Se3 layer using an innovative sulfurization configuration. We find that the crystals of the Sb2Se3 films are reconstructed by post-treatment with sulfur gas, yielding high-quality Sb2Se3 with benign [hkl] growth orientation, a smooth surface, and large compact crystal grains. Moreover, this engineering strategy remarkably mitigates the device open-circuit voltage deficit because of the effectively healed deep level defects. As a result, photovoltaic devices subjected to this post-treatment exhibit markedly improved performance compared to controlled solar cells. This study demonstrates a new sulfurization approach for optimizing the crystallinity and deep-level defects and overall efficiency of Sb2Se3 solar cells.