Unveiling the Impact of Electron Transport Layer and Hole Transport Layer Variations on Cs-Based Perovskite Solar Cells: A Combined Electrical and Optical Simulation Approach

Abstract

Perovskite solar cells (PSCs) have gained significant attention due to their high-power conversion efficiencies (PCE) and versatile material properties. This study uses advanced simulations with OghmaNano to explore the influence of electron transport layers (ETLs) and hole transport layers (HTLs) in cesium-based PSCs, specifically with Cs₂AgBiBr₆ as the absorber material. By analyzing ZnO, SnO₂, and TiO₂ as ETLs and NiOx and Cu₂O as HTLs, this study determines the impact of layer properties and thickness on critical performance metrics, including PCE, V_oc, and J_sc. The study's simulations reveal that optimal absorber layer thicknesses are 100 nm for ZnO and SnO₂ and 400 nm for TiO₂, achieving a peak PCE of 17.11% in the TiO₂/Cu₂O configuration. This study also observes that SnO₂-based devices exhibit superior charge extraction capabilities due to reduced trap states, leading to a more stable voltage output. Additionally, photon recycling effects in Cs₂AgBiBr₆ increase J_sc by up to 5%, a novel finding for cesium-based PSCs. Energy-level alignment analysis shows that TiO₂/Cu₂O minimizes recombination, enhancing fill factor and efficiency. Photon density distribution and energy-level spectra reveal the interplay between optical absorption, charge dynamics, and interface energetics, guiding device architecture optimization. These findings offer key insights for improving lead-free perovskite photovoltaics, enhancing efficiency and stability in future applications.