Solar brilliance unleashed: Maximizing performance of novel carbon-based Rb-doped CsSnI3 perovskite solar cells by gradient doping

Abstract

The commercialization of state-of-the-art perovskite solar cells (PSCs) is hindered by lead toxicity, high production costs, and stability issues. The current study addresses these challenges by exploring lead-free Rb-doped CsSnI3 perovskite with carbon-based materials. Herein, the impact of Rb-doping in CsSnI3 perovskite has been thoroughly investigated on its structural, electrical, and optical properties via DFT studies. The results show that the incorporation of Rb-cation into CsSnI3 significantly enhances the stability of the perovskite active layer (PAL), addressing the major challenge of degradation under environmental conditions. Further, DFT results are used to investigate the potential of Cs0.75Rb0.25SnI3 as a PAL in device architecture FTO/ETL/Cs0.75Rb0.25SnI3/CNTs/C via SCAPS-1D with different electron transport layer (ETL) and carbon-based hole transport layer and back contact. Simulation results show that among different ETLs, WO3 demonstrates the best performance. Further, we have employed a gradient doping (GD) strategy in PAL, dividing it into two sub-layers of thickness 200 nm each with different doping concentrations in the simulated device FTO/WO3/CsRbSnI3/CNTs/C. The aim of implementing GD is to strengthen the electric field and improve the energy band alignments which helps in reducing interfacial recombination. Besides, the impact of band-gap, interfacial defects, hysteresis effect, and C–V and C–F analysis are examined. The results reveal that at doping gradient G = 300, the device attains the best PCE of 19.05% with Eg of 1.32 eV (PAL-1) and 1.22 eV (PAL-2). This study can serve as a benchmark for developing high-performance and low-cost CsRbSnI3-based PSCs utilizing a gradient doping strategy.