Bandgap reduction and efficiency enhancement in Cs 2 AgBiBr 6 double perovskite solar cells through gallium substitution.

Lead-free halide double perovskite (LFHDP) Cs 2 AgBiBr 6 has emerged as a promising alternative to traditional lead-based perovskites (LBPs), offering notable advantages in terms of chemical stability and non-toxicity. However, the efficiency of Cs 2 AgBiBr 6 solar cells faces challenges due to their wide bandgap ( E g ). As a viable strategy to settle this problem, we consider optimization of the optical and photovoltaic properties of Cs 2 AgBiBr 6 by Gallium (Ga) substitution. The synthesized Cs 2 Ag 0.95 Ga 0.05 BiBr 6 is rigorously characterized by means of X-ray diffraction (XRD), UV-vis spectroscopy, and solar simulator measurements. XRD analysis reveals shifts in peak positions, indicating changes in the crystal lattice due to Ga substitution. The optical analysis demonstrates a reduction in the E g , leading to improvement of the light absorption within the visible spectrum. Importantly, the Cs 2 Ag 0.95 Ga 0.05 BiBr 6 solar cell exhibits enhanced performance, as evidenced by higher values of open circuit voltage ( V oc ), short-circuit current ( J sc ), and fill factor (FF), which are 0.94 V, 6.01 mA cm -2 , and 0.80, respectively: this results in an increased power conversion efficiency (PCE) from 3.51% to 4.52%. This research not only helps to overcome film formation challenges, but also enables stable Cs 2 Ag 0.95 Ga 0.05 BiBr 6 to be established as a high-performance material for photovoltaic applications. Overall, our development contributes to the advancement of environmentally friendly solar technologies.