An In-Depth Investigation of the Combined Optoelectronic and Photovoltaic Properties of Lead-Free Cs₂AgBiBr₆ Double Perovskite Solar Cells Using DFT and SCAPS-1D Frameworks

In the backdrop of today's environmental priorities, where toxicity and stability hinder lead-based perovskite solar cell (PSC) progress, the emergence of lead-free alternatives like Cs2AgBiBr6 perovskites has gained significance. This study revolves around the comprehensive evaluation of Cs2AgBiBr6 as a potential photovoltaic (PV) material, using density functional theory (DFT) calculations with CASTEP. Revealing a vital bandgap of 1.654 eV and emphasizing the contributions of Ag-4d and Br-4p orbitals, this analysis also underscores Ag atoms' dominance in charge distribution. Optically, Cs2AgBiBr6 exhibits UV absorption peaks around 15 eV, intensifying with photon energy up to 3.75 eV, hinting at its promise for solar applications. Guided by DFT, forty configurations involving various electron transport layers (ETLs) and hole transport layers (HTLs) are explored. Among these, CNTS emerges as the prime HTL due to ideal absorber alignment. The spotlight architecture, FTO/AZnO/Cs2AgBiBr6/CNTS/Au, boasts exceptional efficiency (23.5%), V-oc (1.38 V), J(sc) (21.38 mA cm(-2)), and FF (79.9%). In contrast, FTO/CdZnS/Cs2AgBiBr6/CNTS/Au achieves a slightly lower 23.15% efficiency. Real-world intricacies are probed, encompassing resistances, temperature, current-voltage (J-V) traits, and quantum efficiency (QE), enhancing practical relevance. These findings are thoughtfully contextualized within prior literature, showcasing the study's contributions to non-toxic, inorganic perovskite solar technology. This work aspires to positively steer sustainable PV advancement.