Chalcogen-Driven Lattice Softening and Bandgap Engineering in CuAlX2 (X = S, Se, Te) Chalcopyrites for Photovoltaic and Thermoelectric Energy Conversion
Solar RRL, cilt.10, sa.19, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 10 Sayı: 19
- Basım Tarihi: 2026
- Doi Numarası: 10.1002/solr.70506
- Dergi Adı: Solar RRL
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Compendex, Environment Index, INSPEC
- Anahtar Kelimeler: BoltzTraP, chalcopyrite semiconductors, density functional theory, elastic properties, electronic structure, optical properties, photovoltaics, thermoelectric materials, VASP calculations
- Recep Tayyip Erdoğan Üniversitesi Adresli: Evet
Özet
Chalcogen substitution provides an effective strategy for simultaneously tuning the lattice dynamics, electronic structure, optical response, and transport behavior of chalcopyrite semiconductors. In this work, density functional theory (DFT) calculations are employed to establish the composition–property relationships governing CuAlX2 (X = S, Se, Te). All three compounds retain the tetragonal (Formula presented.) structure and are dynamically stable, as demonstrated by phonon spectra without imaginary modes. Replacing S with Se and Te progressively expands and softens the lattice, reducing the bulk modulus from 82.50 to 50.45 GPa, Young's modulus from 120.34 to 77.99 GPa, and the Debye temperature from 465.3 to 269.3 K. This lattice softening is accompanied by a chalcogen-induced narrowing of the direct Γ-point Perdew–Burke–Ernzerhof (PBE) bandgap from 1.68 eV in CuAlS2 to 1.04 and 1.01 eV in CuAlSe2 and CuAlTe2, respectively.Because no hybrid-functional, GW, scissor, or spin–orbit correction was applied, these semilocal-DFT gaps are interpreted as screening values rather than quantitative photovoltaic device gaps. The optical spectra show a red-shifting absorption edge and intrinsic absorption coefficients above 105 cm−1; however, absorption strength alone does not determine solar-cell efficiency. Boltzmann-transport calculations within the constant-relaxation-time approximation (CRTA) reveal strong composition-dependent trends in S, σ/τ, and κe/τ. Since lattice thermal conductivity was not explicitly calculated, a conventional total thermoelectric figure of merit is not claimed; an electronic-only ZTe ratio is used only as a screening indicator. Overall, the results establish composition-dependent trends that motivate CuAlS2, CuAlSe2, and CuAlTe2 for further optoelectronic and thermoelectric screening, subject to higher-level electronic-structure calculations and experimental/device-level validation.