Er3+ substitution as route to boost optoelectronic and thermoelectric performance of double perovskites Cs2AgAs1-xErxBr6: Insights from DFT

초록

A systematic investigation is carried out for double perovskites Cs2AgAs1-xErxBr6 with x = 0.00, 0.25 and 0.50 to explore the more suitable materials for optoelectronic and thermoelectric applications. The structural analysis reveals that both the pristine Cs2AgAsBr6 as well as the Er substituted versions (25-50%) crystallize in face centered cubic (FCC) form with lattice constants 9.85, 9.95, and 10.08 A. The structural stability is assessed from the Goldschmidt's factors, the thermodynamic stability from formation energies (negative values) while the compliance of Born-Huang criteria assure the mechanical stability. The observed band gap energies are 2.42, 2.45, and 2.54 eV with direct band gap nature. The strong optical absorption (peak height similar to 10(6) cm(-1)) in the visible range (at 2.65, 2.72, and 2.75 eV) highlights the suitability for optoelectronic applications. Furthermore, the values of figure of merit ZT increases with increase of Er doping i.e. 0.95, 0.97, and 0.98 for Cs2AgAs1-xErxBr6 with x = 0.00, 0.25 and 0.50 respectively at 300 K. Therefore, the Er doping not only reduces toxicity but also enhances optoelectronic and thermoelectric efficiency while preserving the stability of the materials.