Effect of CrF₃ Addition on Photoluminescence Properties of Lead-Free Cs₄SnBr_6-xF_x Zero-Dimensional Perovskite

Zero-dimensional (0D) tin halide perovskites, characterized by their broadband and adjustable emissions, high photoluminescence quantum yield, and absence of self-absorption, are crucial for the fabrication of high-efficiency optoelectronic devices, such as LEDs, solar cells, and sensors. Despite these attributes, boosting their emission efficiency and stability poses a significant challenge. In this work, Cr³⁺-doped Cs₄SnBr_6-xF_x perovskites were synthesized using a water-assisted wet ball-milling method. The effect of CrF₃ addition on photoluminescence properties of Cs₄SnBr_6-xF_x Perovskites was investigated. We found that Cr³⁺-doped Cs₄SnBr_6-xF_x Perovskites exhibit a broad emission band, a substantial Stokes shift, and an efficient green light emission centered at about 525 nm at ambient temperature. The derived photoluminescence quantum yield amounted to as high as 56.3%. In addition, these Cr³⁺-doped Cs₄SnBr_6-xF_x perovskites outperform their undoped counterparts in terms of thermal stability. Through a comprehensive analysis of photoluminescence measurements, our findings suggested that the elevated photoluminescence quantum yield can be attributed to the enhanced exciton binding energy of self-trapped excitons (STEs) and the suitable electron-phonon coupling resulting from the substantial distortion of [SnBr₆]^4- octahedra instigated by the addition of CrF₃.