Computational study of narrow bandgap double halide perovskites Rb₂TlRhX₆ (X=Cl, Br, I) for energy harvesting applications

Abstract First-principles density functional theory (DFT) was applied to study the structure, mechanical, and optoelectronic properties of a double halide perovskite Rb 2 TlRhX 6 (X=Cl, Br, I) in the cubic Fm <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mo>̅</mml:mo> </mml:mover> </mml:math> m space group 225. The stability of such perovskite alloys is established by evaluating the stability metrics with formation energy. The ductile nature of these materials suggests they are ideal candidates for flexible optoelectronic and photovoltaic devices. Most of the halide perovskites display higher values of optical band gaps, however, the proposed Rb 2 TlRhX 6 (X=Cl, Br, I) compounds in the present communication reveal direct narrow bandgap values 1.56 eV, 1.44 eV, 1.32 eV for Cl, Br and I halides respectively by applying TB-mBJ potential. The strong optical absorption, excellent conductivity, and poor reflectivity as disclosed by the investigated materials have great potential for optoelectronic applications. The study successfully computed the Spectroscopic Limited Maximum Efficiency (SLME) for the investigated materials. Utilizing the values of direct bandgap and theoretical absorption coefficients, yielding efficiency values of Rb 2 TlRhCl 6 , Rb 2 TlRhBr 6 , and Rb 2 TlRhI 6 as 29.42%, 28.53%, and 29.91% respectively at 26 °C. The present research demonstrates that the SLME model is a promising and effective approach to calculating PCEs and providing useful insights into the field of photovoltaic research.