Study of elastic, structural, thermoelectric and optoelectronics characteristics of Na ₂ YCuX ₆ (X = Br, Cl) halide double perovskites

Abstract

Abstract The structural, electronic, optical, elastic, and thermoelectric (TE) characteristics of Na 2 YCuX 6 (X = Br, Cl) halide double-perovskites (HDPs) were investigated by using first principle approach within WIEN2K code. Perdew, Burke and Ernzerhof generalized-gradient approximation (PBEsol-GGA) with modified Becke-Johnson (mBJ) potential were used in the current investigations. Enthalpy of formation energies (E f ) determined for Na 2 YCuBr 6 and Na 2 YCuCl 6 were −2.29 and −1.955 eV, correspondingly which verify the stability of both compounds. Na 2 YCuBr 6 is discovered to be semiconducting with indirect bandgap (E g ) of 2.492 and Na 2 YCuCl 6 has direct E g of 2.571 eV. Absorption coefficient shows largest values at 5.74 and 6.92 eV for Na 2 YCuBr 6 and Na 2 YCuCl 6 , correspondingly, which lie in UV range. Pugh’s ratio (B/G) values were calculated as 2.00 and 4.62 for Na 2 YCuCl 6 and Na 2 YCuBr 6 , correspondingly which ensure the ionic bond and ductile characteristics of the compounds. From the TE calculations, ZT shows maximum values of 0.74 and 0.73 for Na 2 YCuBr 6 and Na 2 YCuCl 6 , respectively. Results showed that investigated materials are efficient candidates for optoelectronic and TE appliances.