Characterizing defect levels and identifying the compositional elements in semiconducting materials are important research subject for understanding the mechanism of photogenerated carrier recombination and reducing energy loss during solar energy conversion. Here it shows that deep‐level defect in antimony triselenide (Sb2Se3) is sensitively dependent on the stoichiometry. For the first time it experimentally observes the formation of amphoteric SbSe defect in Sb‐rich Sb2Se3. This amphoteric defect possesses equivalent capability of trapping electron and hole, which plays critical role in charge recombination and device performance. In comparative investigation, it also uncovers the reason why Se‐rich Sb2Se3 is able to deliver high device performance from the defect formation perspective. This study demonstrates the crucial defect types in Sb2Se3 and provides a guidance toward the fabrication of efficient Sb2Se3 photovoltaic device and relevant optoelectronic devices.

Here we demonstrate that thiophene modified quinoxaline core small molecule is able to be applied in Sb2(S,Se)3 solar cells. We reveal that interaction between thiophene and Sb2(S,Se)3 through Sb-S bond...

Thermal treatment of inorganic thin films is a general and necessary step to facilitate crystallization and, in particular, to regulate the formation of point defects. Understanding the dependence of the defect formation mechanism on the annealing process is a critical challenge in terms of designing material synthesis approaches for obtaining desired optoelectronic properties. Herein, a mechanistic understanding of the evolution of defects in emerging Sb2(S,Se)3 solar cell films is presented. A top‐efficiency Sb2(S,Se)3 solar‐cell film is adopted in this study to consolidate this investigation. This study reveals that, under hydrothermal conditions, the as‐deposited Sb2(S,Se)3 film generates defects with a high formation energy, demonstrating kinetically favorable defect formation characteristics. Annealing at elevated temperatures leads to a two‐step defect transformation process: 1) formation of sulfur and selenium vacancy defects, followed by 2) migration of antimony ions to fill the vacancy defects. This process finally results in the generation of cation–anion antisite defects, which exhibit low formation energy, suggesting a thermodynamically favorable defect formation feature. This study establishes a new strategy for the fundamental investigation of the evolution of deep‐level defects in metal chalcogenide films and provides guidance for designing material synthesis strategies in terms of defect control.

Obtaining high‐quality absorber layers is a major task for constructing efficient thin‐film solar cells. Hydrothermal deposition is considered a promising method for preparing high‐quality antimony sulfide (Sb2S3) films for solar cell applications. In the hydrothermal process, the precursor reactants play an important role in controlling the film formation process and thus the film quality. In this study, Sb2O3 is applied as a new Sb source to replace the traditional antimony potassium tartrate to modulate the growth process of the Sb2S3 film. The reaction mechanism of the transition from Sb2O3 to Sb2S3 in the hydrothermal process is revealed. Through controlling the nucleation and deposition processes, high‐quality Sb2S3 films are prepared with longer carrier lifetimes and lower deep‐level defect densities than those prepared from the traditional Sb source of antimony potassium tartrate. Consequently, a solar cell device based on this improved Sb2S3 delivers a high power conversion efficiency of 6.51 %, which is in the top tier for Sb2S3‐based solar devices using hydrothermal methods. This research provides a new and competitive Sb source for hydrothermal growth of high‐quality antimony chalcogenide films for solar cell applications.