Investigating optical, electronic, and thermoelectric properties of X2ScIO6 (X = K, Rb, and Cs) double perovskite semiconductors for green energy applications

We present our findings on the structural, optical, electronic, and thermoelectric characteristics of X₂ScIO₆ (X = K, Rb, and Cs) double perovskites using density functional theory (DFT) and post-DFT calculations. The calculated tolerance factor values exhibit the structural stability of these double perovskites, whereas negative values of the formation energy and Gibbs free energy verify their thermodynamic stability. Energy band structure calculations reveal the semiconducting nature of these perovskites with band gaps of 1.37, 1.03, and 0.55 eV for K₂ScIO₆, Rb₂ScIO_6, and Cs₂ScIO₆ respectively. These double perovskites could achieve higher optical absorption in the ultraviolet region beyond 5 eV. The Seebeck coefficient’s positive value indicates these compounds’ p-type nature. Their figure of merit values are greater than the other conventional double perovskites and therefore could be efficiently utilized in thermoelectric applications at elevated temperatures.