Study of lead free double perovskites Na2XAgCl6 (X = Ga, In Tl) for solar cells and transport applications

The double perovskites are rich merchant to harvest energy from solar cells and thermoelectric generators to cover up its shortfall. Therefore, in this article, the electronic, optical, and thermoelectric characteristics of Na2XAgCl6 (X = Ga, In Tl) are briefly elaborated. The tolerance and octahedral factors are calculated for structural stability and formations energy for thermodynamically existence. The band structures are show the tuning of band gap from 2.57 eV to 1.30 eV by the changing cations from Ga to Tl. The density of states shows the p-d hybridization among X, Ag and Cl ions is responsible for decreasing band gap. The optical analysis in terms of dielectric constant, absorption and other dependent parameters illustrate broad absorption bands in ultraviolet region (Ga, In) and in visible region (Tl). The shifting of absorption zone to visible region increase their potential for solar cells. Thermoelectric calculations have been performed to evaluate the electrical conductivity, Seebeck coefficient, and thermal conductivity by BoltzTraP code. The large figure of merit and extremely small lattice thermal conductivity at room temperature also make them important for thermoelectric generators fabrication to harvest heat energy.