Three-Dimensional Optical-Electrical Simulation of Cs2AgBiBr6 Double Perovskite Solar Cells

TL;DR

This study uses 3D finite-element simulations to optimize Cs2AgBiBr6 double perovskite solar cells, achieving a theoretical efficiency of 31.76%, surpassing previous experimental and numerical results.

Contribution

First comprehensive 3D FEM-based analysis of double halide perovskite solar cells, identifying optimal transport layers and device parameters for maximum efficiency.

Findings

Optimal ETL and HTL identified as CeO2 and P3HT.

Simulated maximum PCE of 31.76%.

Device performance highly sensitive to layer thickness and defect densities.

Abstract

Despite significant advances in lead-free perovskite photovoltaics, achieving a balance among environmental safety and high optoelectronic performance remains challenging. The inorganic double perovskite Cs2AgBiBr6 has emerged as a promising candidate owing to its robust three-dimensional crystal structure and suitable visible-range bandgap. However, best power conversion efficiencies (PCEs) for Cs2AgBiBr6 solar cells reported so far - 6.37% experimentally and 27.78% in numerical studies - remain below the theoretical performance potential, largely due to suboptimal charge transport layers, and interface-related recombination losses. Here, we address this gap using a 3D finite-element method (FEM) implemented in COMSOL Multiphysics, which couples optical simulations with semiconductor drift-diffusion transport. To our knowledge, this work represents the first comprehensive 3D FEM-based study of a double halide perovskite solar cell. Screening of 25 electron transport layer (ETL)-hole transport layer (HTL) combinations identifies CeO2 and P3HT as the optimal ETL and HTL respectively. Device performance is further analyzed through systematic variation of layer thicknesses, doping concentrations and defect densities within the FTO/CeO2/Cs2AgBiBr6/P3HT/Au architecture. Under optimized parameters, the simulated device achieves a PCE of 31.76%, representing the theoretical upper bound predicted by the model. Overall, this work demonstrates 3D physics-based device engineering as a decisive pathway for overcoming efficiency bottlenecks in lead-free double perovskite photovoltaics.