Work

First-principles investigations on the structural and optoelectronic properties of CdGa2X4 (X = S, Se, Te) for the photovoltaic applications

Year: 2026

Type: article

Abstract: This study presents a comprehensive first-principles investigation of the structural, elastic, electronic, and optical properties of the defect-chalcopyrite compounds CdGa 2 X 4 (X = S, Se, Te) using density functional theory (DFT) within the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) functional, complemented by SCAPS-1D device simulations to evaluate their photovoltaic performance. All compounds satisfy the Born stability criteria and exhibit elastic anisotropy, with CdGa 2 Se 4 showing the largest universal anisotropy index ( 𝐴 𝑈 = 2 . 1 2 9 ). The calculated direct band gaps decrease systematically from 2.14 eV (CdGa 2 S 4 ) to 1.03 eV (CdGa 2 Te 4 ), accompanied by strong anisotropy in the carrier effective masses with hole-to-electron mass ratios reaching up to 15.35 in the in-plane direction. Exciton binding energies estimated from the effective masses and static dielectric constants are ∼ 23.5 meV for CdGa 2 S 4 and ∼ 8.4–8.5 meV for CdGa 2 Se 4 and CdGa 2 Te 4 . The larger binding energy in CdGa 2 S 4 favors light-emitting applications, whereas the smaller values in the Se and Te compounds promote free-carrier photovoltaic operation. The dielectric function, absorption coefficient, and refractive index exhibit directional anisotropy between the in-plane and out-of-plane directions. The band gap of CdGa 2 Se 4 (1.48 eV) lies close to the Shockley–Queisser optimum, making it particularly attractive for single-junction thin-film solar cell applications. Using these DFT-derived parameters as absorber-layer inputs, SCAPS-1D simulations of an 𝑛 -CdS/ 𝑝 -CdGa 2 X 4 / 𝑝 + -WSe 2 heterojunction solar cell yield a maximum power conversion efficiency (PCE) of 28.56% at a low defect density of 1 × 1 ⁢ 0 1 4 cm −3 , decreasing to a more conservative 24.16% when the absorber defect density is increased to 1 × 1 ⁢ 0 1 6 cm −3 , a defect-density range relevant to early-stage thin-film absorbers. CdGa 2 Se 4 consistently outperforms CdGa 2 Te 4 across this defect-density range, identifying it as the more promising absorber for thin-film photovoltaic applications. Overall, the results establish composition-dependent structure–property relationships in CdGa 2 X 4 and highlight their potential for optoelectronic and photovoltaic applications.

Source: Next Materials

DOI: 10.1016/j.nxmate.2026.103351