Hasan Mohammed Mehedi, Hasan Nazmul, Kabir Alamgir
Department of Theoretical Physics, University of Dhaka, Dhaka 1000, Bangladesh.
Department of Electrical and Computer Engineering, North South University, Dhaka, Bangladesh.
R Soc Open Sci. 2025 Apr 30;12(4):241680. doi: 10.1098/rsos.241680. eCollection 2025 Apr.
Halide double perovskites have various benefits over lead-based perovskites due to their suitable optical absorption efficiency, higher stability, tunable bandgap, large carrier mobility, easy availability and low cost. The structural, electrical, optical and mechanical characteristics of the lead-free halide double perovskites CsNaTlBr Cl ( = 0, 1, 2, 3, 4, 5 and 6) are investigated by utilizing the first-principles density functional theory (DFT). The structural properties were computed at equilibrium, revealing that the crystals undergo structural phase transitions as the doping concentration varies. However, crystal stability was confirmed through the evaluation of the tolerance factor. The Heyd-Scuseria-Ernzerhof (HSE06) functional is used to correct the bandgap underestimation by generalized gradient approximation with Perdew-Burke-Ernzerhof (GGA-PBE). The band edge profile and electron density of states confirm the direct-bandgap semiconducting nature of the compounds. The bandgap increases approximately linearly with Cl incorporation, sharply tuned from 0.80 to 1.75 eV (GGA-PBE) and 1.78 to 2.98 eV (HSE06), making them highly suitable for photovoltaic and optoelectronic applications. The effective mass of the electron ranges from 0.283 to 0.449 m, and the carrier mobility is from 83.913 to 305.485 cmVs, respectively, suggesting excellent charge transport characteristics, essential for high-performance solar cells and photodetectors. The considered NaTl-based double perovskites have strong optical absorption in the visible and UV spectrum, with enhanced conductivity as Cl content increases. Binding energy analysis confirms strong lattice stability, with values decreasing from -3.193 eV (Br-rich) to -3.559 eV (Cl-rich), indicating improved thermodynamic robustness as Cl concentration increases. Mechanical analysis shows the ductile behaviour of the considered perovskites, supported by Poisson's ratio and Pugh's modulus. The rising bulk modulus and Debye temperature with Cl incorporation enhance rigidity and thermal stability. These insights advance the anion-engineered design of stable, high-efficiency, lead-free NaTl-based perovskites for next-generation optoelectronic applications.
卤化物双钙钛矿由于其合适的光吸收效率、更高的稳定性、可调节的带隙、大的载流子迁移率、易于获取和低成本等优点，相对于铅基钙钛矿具有多种优势。利用第一性原理密度泛函理论（DFT）研究了无铅卤化物双钙钛矿CsNaTlBrCl （ = 0、1、2、3、4、5和6）的结构、电学、光学和力学特性。在平衡状态下计算了结构性质，结果表明随着掺杂浓度的变化，晶体经历结构相变。然而，通过容忍因子的评估证实了晶体的稳定性。使用Heyd-Scuseria-Ernzerhof（HSE06）泛函来校正由Perdew-Burke-Ernzerhof（GGA-PBE）广义梯度近似导致的带隙低估。带边轮廓和电子态密度证实了这些化合物的直接带隙半导体性质。随着Cl的掺入，带隙近似线性增加，从0.80 eV急剧调谐到1.75 eV（GGA-PBE）和从1.78 eV调谐到2.98 eV（HSE06），这使得它们非常适合用于光伏和光电子应用。电子的有效质量范围为0.283至0.449 m，载流子迁移率分别为83.913至305.485 cm²V⁻¹s⁻¹，表明具有优异的电荷传输特性，这对于高性能太阳能电池和光电探测器至关重要。所考虑的基于NaTl的双钙钛矿在可见光和紫外光谱中具有强烈的光吸收，随着Cl含量的增加导电性增强。结合能分析证实了强晶格稳定性，其值从-3.193 eV（富Br）降至-3.559 eV（富Cl），表明随着Cl浓度的增加热力学稳定性得到改善。力学分析表明所考虑的钙钛矿具有延性，泊松比和普氏模量支持这一结论。随着Cl的掺入，体积模量和德拜温度升高，增强了刚性和热稳定性。这些见解推动了用于下一代光电子应用的稳定、高效、无铅NaTl基钙钛矿的阴离子工程设计。
