A comprehensive investigation into the structural, elastic, optoelectronic, and thermoelectric properties of Cs2B′B″I6 halide double perovskites (DPs), where B′B″ represents various combinations, including BeCa, BeSr, GeCd, GeBe, and GeMg, is conducted. Using the full‐potential linearized augmented plane wave approach within the density functional theory framework, this analysis confirms the materials’ structural and dynamic stabilities through negative formation energies and adherence to elastic constant stability criteria. The generalized gradient approximation and the modified Becke–Johnson (mBJ) potential for electronic structure calculations are utilized. Notably, Cs2B′B″I6 DPs with B′B″ as BeCa or BeSr exhibit direct bandgaps (Γ–Γ), while those with B′B″ as GeCd, GeBe, or GeMg display indirect bandgaps (X–L). These findings offer valuable insights into the potential use of these materials in photovoltaic and optoelectronic devices. Furthermore, the exploration of thermoelectric properties, covering electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and figure of merit at temperatures of 300, 600, and 900 K, suggests that Cs2B′B″I6 DPs, regardless of the specific B′B″ composition (BeCa, BeSr, GeCd, GeBe, GeMg), holds promise for applications in thermoelectric devices.

中文翻译：

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Cs2B′B″I6 (B′B″: BeCa, BeSr, GeCd, GeBe, GeMg) 卤化物双钙钛矿用于最佳太阳能电池和可再生能源应用的密度泛函理论探索

全面研究Cs的结构、弹性、光电和热电性质2B′B″I6进行了卤化物双钙钛矿（DP），其中 B'B'' 代表各种组合，包括 BeCa、BeSr、GeCd、GeBe 和 GeMg。该分析使用密度泛函理论框架内的全势线性化增强平面波方法，通过负形成能和遵守弹性常数稳定性标准确认了材料的结构和动态稳定性。利用广义梯度近似和修正的 Becke-Johnson (mBJ) 势进行电子结构计算。值得注意的是，铯2B′B″I6具有 B'B" 为 BeCa 或 BeSr 的 DP 表现出直接带隙 (Г–Г)，而具有 B'B" 作为 GeCd、GeBe 或 GeMg 的 DP 表现出间接带隙 (X–L)。这些发现为这些材料在光伏和光电设备中的潜在用途提供了宝贵的见解。此外，对热电性质的探索，包括电导率、塞贝克系数、电子热导率以及 300、600 和 900 K 温度下的品质因数，表明 Cs2B′B″I6无论特定的 B′B″ 成分（BeCa、BeSr、GeCd、GeBe、GeMg）如何，DP 都有望在热电器件中得到应用。