Study of optoelectronic and transport properties of SrCd2X2 (X = P, As, Sb) zintl-phase for renewable energy applications

The Zintl phase is a developing group of materials with considerable potential for use in solar cells and energy harvesting technologies. This study comprehensively investigates the structural, electronic, optical, and thermoelectric characteristics of novel Zintl phase alloys SrCd₂X₂ (X = P, As, Sb) using the density functional theory-based Wien2k code. Thermodynamic and dynamic stability is confirmed by calculating the enthalpy of formation and phonon band structures. The band structure analysis systematically decreased the band gap from 1.32 eV to 0.81 eV and 0.43 eV to replace P with As and Sb, respectively. The interaction between the valence and conduction band edges of the p- and d-states of X and Cd is essential for modulating the band gaps and other physical characteristics. The observed high absorption coefficient with absorption bands in the visible and infrared regions suggests the potential for optoelectronic and IR detectors. Notably, the 1.32 eV bandgap of SrCd₂P₂ is well within the ideal bandgap range for solar cell applications. Furthermore, applying the BoltzTrap code, the transport properties are evaluated, revealing a low thermal conductivity (0.2–1.7 W/mK) along with a reasonable Seebeck coefficient (242–268 µV/K) and power factor (2.3 W/mK²). These findings collectively indicate promising thermoelectric performance.