Exploration of lead-free novel double perovskite halides Na2TlBiX6 (X = Cl, Br, I) for flexible memory devices: Using DFT approach

Abstract

Flexible resistive switching random access memory (RRAM) devices have drawn significant attention due to their low power consumption, high speed and simple structure. Halide perovskites with excellent optoelectronic properties such as high charge carrier mobility and tunable bandgap emerge as the best material for flexible RRAM devices. In this study, for the first time, the structural, mechanical, optoelectronic and thermoelectric properties of Na2TlBiX6 (X = Cl, Br, I) were explored using the Wien2k package for flexible RRAM devices. Elastic parameters show that studied perovskites display mechanical stability, ductile nature and anisotropic behaviour with lower values of the bulk modulus. In comparison, Na2TlBiI6 has a smaller bulk modulus which makes it a suitable material for flexible RRAM devices. Furthermore, the large machinability index of Na2TlBiI6 among the studied perovskites highlights its feasibility for industrial applications. The semiconductor nature of Na2TlBiX6 (X = Cl, Br, I) is confirmed from band structure, total density of states (TDOS) and partial density of states (PDOS) calculation. The optical study shows that Na2TlBiI6 can absorb a wide range of ultraviolet and visible electromagnetic incident radiations making it an excellent material for flexible RRAM devices. Lastly, in terms of transport properties at room temperature, Na2TlBiI6 reveals a larger figure of merit (ZT) than other studied perovskites making it a suitable candidate for thermoelectric applications. The outcome of this study suggests that Na2TlBiI6 is the perfect candidate for flexible RRAM devices at room temperature.