Changcheng Chen

Lead-free vacancy-ordered double perovskites offer a compositional platform for exploring wavelength-dependent optical responses. Here, the structural, mechanical, electronic, and optical properties of Cs2TiI6, Cs2ZrI6, Cs2HfI6, and Cs2ZrCl6 are compared using PBE-based density functional theory. The calculated structures satisfy the cubic elastic stability criteria and exhibit negative formation energies relative to the reference states used. Their calculated bandgaps are 0.85, 1.76, 2.16, and 3.69 eV, respectively. Projected density-of-states and electron-localization analyses relate the composition-dependent electronic structure to metal–halogen bonding within isolated octahedra. The calculated absorption spectra shift toward higher photon energies across this sequence, while the static refractive index decreases from 2.55 to 1.85. These results support a qualitative assessment of Cs2TiI6 for near-infrared harvesting, Cs2ZrI6 for indoor visible-light absorption, Cs2HfI6 for wavelength-dependent visible photodetection, and Cs2ZrCl6 for ultraviolet-selective optical applications. The proposed device architectures and scintillation pathway are conceptual prospects rather than quantitatively simulated or experimentally demonstrated devices. This study provides a comparative basis for selecting compositions by their electronic and optical properties, while quantitative device performance and excited-state mechanisms remain to be validated.

Lead-free halide double perovskites are promising candidates for ultraviolet (UV) optoelectronic applications because of wide band gaps, compositional tunability, and relatively high structural stability. Here, a target-oriented materials-screening framework integrating machine learning, composition- and geometry-based rules, Materials Project validation, and first-principles calculations was developed. Band-gap prediction models were constructed using 1,193 inorganic perovskite records, and the initial chemical space was progressively narrowed to eight A2BB′X6 candidates. All eight materials satisfy the Born mechanical-stability criteria and exhibit positive minimum eigenvalues of their elastic stiffness matrices. Ab initio molecular dynamics simulations further support the finite-temperature structural stability of four representative Cl-based systems at 300 K, while phonon calculations indicate no significant dynamical instability for Cs2AgScCl6 and Cs2NaInCl6. PBE calculations reveal wide-band-gap semiconducting behavior, with the valence-band edges dominated primarily by halogen p states and the conduction-band edges derived mainly from B/B′-site metal orbitals. PBE+SOC calculations for three representative heavy-element systems show material-dependent band-gap narrowing, motivating the extension of HSE06 validation to all eight candidates. The HSE06 band gaps range from 4.0075 to 5.0159 eV, placing all candidates within the UV energy range. Optical calculations show weak visible-light response and pronounced UV absorption, whereas effective-mass and elastic-anisotropy analyses reveal distinct carrier-transport and mechanical-response characteristics. Among the candidates, Cs2NaInCl6 provides a favorable balance of direct-gap character, UV absorption, electron transport, finite-temperature structural stability, and mechanical adaptability. These findings provide a systematic basis for prioritizing lead-free double perovskites for UV optoelectronic applications.

High-throughput screening identifies WSi ₂ N ₄ to construct a direct Z-scheme WSi ₂ N ₄ /Ti ₂ CO ₂ heterojunction. NAMD confirms ultrafast interfacial recombination, yielding 25.5% solar-to-hydrogen efficiency and spontaneous overall water splitting.

Sn-based perovskite is considered to be the most promising environmentally friendly alternative material because of its low toxicity and photoelectric properties similar to lead-based perovskite.

Lead-free halide double perovskites are promising candidates for ultraviolet (UV) optoelectronic applications because of wide band gaps, compositional tunability, and relatively high structural stability. Here, a target-oriented materials-screening framework integrating machine learning, composition- and geometry-based rules, Materials Project validation, and first-principles calculations was developed. Band-gap prediction models were constructed using 1,193 inorganic perovskite records, and the initial chemical space was progressively narrowed to eight A2BB′X6 candidates. All eight materials satisfy the Born mechanical-stability criteria and exhibit positive minimum eigenvalues of their elastic stiffness matrices. Ab initio molecular dynamics simulations further support the finite-temperature structural stability of four representative Cl-based systems at 300 K, while phonon calculations indicate no significant dynamical instability for Cs2AgScCl6 and Cs2NaInCl6. PBE calculations reveal wide-band-gap semiconducting behavior, with the valence-band edges dominated primarily by halogen p states and the conduction-band edges derived mainly from B/B′-site metal orbitals. PBE+SOC calculations for three representative heavy-element systems show material-dependent band-gap narrowing, motivating the extension of HSE06 validation to all eight candidates. The HSE06 band gaps range from 4.0075 to 5.0159 eV, placing all candidates within the UV energy range. Optical calculations show weak visible-light response and pronounced UV absorption, whereas effective-mass and elastic-anisotropy analyses reveal distinct carrier-transport and mechanical-response characteristics. Among the candidates, Cs2NaInCl6 provides a favorable balance of direct-gap character, UV absorption, electron transport, finite-temperature structural stability, and mechanical adaptability. These findings provide a systematic basis for prioritizing lead-free double perovskites for UV optoelectronic applications.