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., Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlTlCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlAgCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, and Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlCuCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, 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 Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlTlCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlAgCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, and Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlCuCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>, respectively. Furthermore, we incorporated PTAA, Spiro-OMeTAD, CuI, CuSCN, NiO, and MoO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sub> as hole-injection layers (HILs)/hole-transport layers (HTLs) and 3P-T2T, ZnO, and Zn<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>SnO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>4</roman></sub> as electron-transport layers (ETLs) to recognize the best HTL/Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlAgCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>/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/Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlAgCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub>/ZnO/LiF/Al, was identified, which exhibited higher recombination in the Rb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>AlAgCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>6</roman></sub> 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.