Highly efficient MAGeI3 HTL-free perovskite solar cell with lithium-doped electron transport layer: A dive into SCAPS-1D simulation insight

This study presents a numerical investigation into the performance of a hole transport layer (HTL)-free perovskite solar cell (PSC) based on MAGeI₃, utilizing a lithium-doped TiO₂ (Li-TiO₂) electron transport layer (ETL). Simulations were conducted using the Solar Cell Capacitance Simulator (SCAPS-1D), which solves the Poisson and continuity equations for electrons and holes under steady-state conditions to model semiconductor device behavior. The optimized device architecture—FTO/Li-TiO₂/MAGeI₃/Au—achieved a power conversion efficiency (PCE) of 13.68%, with a short-circuit current density (Jsc) of 17.07 mA/cm², open-circuit voltage (Voc) of 0.98 V, and a fill factor (FF) of 81.89%. Key design parameters—including an ETL thickness of 0.01 μm, absorber thickness of 3.0 μm, absorber defect density (Nt = 10¹⁴ cm⁻³), and ETL doping concentration (ND = 10²⁰ cm⁻³)—were systematically optimized to suppress recombination and improve charge extraction. Lithium doping in TiO₂ was found to enhance electrical conductivity and reduce interfacial defects, thereby improving electron transport and minimizing carrier recombination. External factors such as temperature, series resistance (Rs), and shunt resistance (Rsh) were analyzed, showing a 10.92% PCE loss, 13.16% PCE loss, and 17.74% gain in PCE at increased temperature, Rs, and Rsh, respectively. This work, thus, highlights the potential of Li-TiO2 as a high-performance ETL and the potential of Ge-based PSCs, offering a pathway toward eco-friendly, cost-effective photovoltaic technologies. The results provide critical insights for future experimental validation and device optimization