The intrinsic problems of toxicity and instability of lead solar cells have motivated extensive research intended to develop alternative materials for photovoltaic applications. First-principles calculations were performed in order to shed light on replacing the Pb²⁺ cation in lead- and mixed-halide materials with a formula of Cs₂X₂Y₂ (X, Y = F, Cl, Br, I). The calculated band gaps range from 0 eV to 3.188 eV, and the absorption coefficients from 6 to 16 × 10⁴ cm⁻¹. The band gap of Cs₂Cl₂I₂ is close to the Shockley-Queisser limit and its absorption coefficient is in the visible frequency range, which, in conjunction with its easy and economical synthesis process, qualify it as an alternative lead-free material for fabricating solar cells. It is suggested for further work that if the ratio of halogens is adjusted then the band gaps of Cs₂F₂Cl₂, Cs₂Cl₂I₂, Cs₂Br₂I₂, and Cs₂I₂F₂ may be tuned to the desired electronic band gap limit required to improve their optoelectronic performance.

铅太阳能电池的毒性和不稳定性的内在问题激发了旨在开发用于光伏应用的替代材料的广泛研究。进行第一性原理计算是为了阐明用Cs ₂ X ₂ Y ₂ (X, Y = F, Cl, Br, I)的分子式替换铅和混合卤化物材料中的 Pb ²⁺阳离子。计算出的带隙范围为 0 eV 至 3.188 eV，吸收系数为 6 至 16 × 10 ⁴ cm ^-1。Cs ₂ Cl ₂ I ₂的带隙接近 Shockley-Queisser 极限，其吸收系数在可见频率范围内，再加上其简单经济的合成工艺，使其成为制造太阳能电池的替代无铅材料。建议用于进一步工作，如果被调整卤素的比率然后Cs的带隙₂ ˚F ₂氯₂，铯₂氯₂我₂，铯₂溴₂我₂和Cs ₂我₂ ˚F ₂可被调谐达到提高其光电性能所需的电子带隙极限。