Polyfluorene incorporation for superior performance and band gap reduction: enhancing Cs2AgBiBr6 double perovskite solar cells

Lead-free halide double perovskites (LFHDPs) based on Cs2AgBiBr6 are a good replacement for traditional lead-based LBPs due to their chemical stability and lack of toxicity. Double perovskite Cs2AgBiBr6-based solar cells have limited efficiency due to a large band gap, suggesting polyfluorene (PF) replacement as a workable solution to enhance their optical and photovoltaic characteristics. PF incorporation-induced crystal structural changes, as demonstrated by peak position shifts in X-ray diffraction. The UV-Vis spectroscopy, and solar simulator tests, were used to study the effect of PF on Cs2AgBiBr6. Optical examination reveals a decrease in E-g, leading to improved light absorption in the visible spectrum. By adding PF to their lattices, we effectively give the weakly luminous Cs2AgBiBr6 double perovskite robust red luminescence. The Cs2Ag0.95PF0.05BiBr6 solar cell has demonstrated a notable enhancement in performance. In that order, its enhanced fill factor, short-circuit current, and open-circuit voltage are 0.81, 5.73mAcm(-2), and 0.93V. Power conversion efficiency (PCE) has improved from 3.75% to 4.26%. About 13.60% of efficiency is increased by PF incorporation. The study identifies Cs2Ag0.95PF0.05BiBr6 as a high-performance material for solar applications and addresses issues with film formation. Our objective is to advance environmentally friendly solar technologies by enhancing efficiency, with future research focusing on interfacial engineering, specifically optimizing electron and hole transport layers. [Graphical Abstract]