Computational Insights Into Rubidium-Based Double Perovskites and Charge-Transport Layer Engineering for High-Efficiency Perovskite LEDs

Rubidium-based double perovskite materials have recently gained excellent attention as a potential material for photovoltaic cells. However, these double perovskites have not been much explored for perovskite light-emitting diodes (LEDs). In this work, we performed a computational study of rubidium-based double perovskites, i.e., Rb2AlTlCl6, Rb2AlAgCl6, and Rb2AlCuCl6, through density functional theory (DFT) using the Cambridge Serial Total Energy Package (CASTEP) to evaluate and compare their electrical and optical properties. The optical characteristics are explained through the analysis of dielectric constants, absorption, refractive index, and reflectivity. The calculated energy bandgap using the generalized gradient approximation-Perdew–Burke–Ernzerhof (GGA-PBE) approach was 3.25, 2.20, and 0.70 eV for Rb2AlTlCl6, Rb2AlAgCl6, and Rb2AlCuCl6, respectively. Furthermore, we incorporated PTAA, Spiro-OMeTAD, CuI, CuSCN, NiO, and MoO3 as hole-injection layers (HILs)/hole-transport layers (HTLs) and 3P-T2T, ZnO, and Zn2SnO4 as electron-transport layers (ETLs) to recognize the best HTL/Rb2AlAgCl6/ETL combination with high efficiency using the SETFOS software. As observed from the simulation study, among 18 device architectures, the best-performing device architecture, ITO/NiO/Rb2AlAgCl6/ZnO/LiF/Al, was identified, which exhibited higher recombination in the Rb2AlAgCl6 emitting layer. In addition, the effect of the perovskite layer, HTL, and ETL thicknesses was also assessed for the best-performing device, along with their corresponding recombination and electric field distribution, outcoupling efficiency, luminance, current efficiency, and external quantum efficiency (EQE). This computational study and device engineering provide a potential route for fabricating high-efficiency perovskite LED.