Bandgap reduction and efficiency enhancement in CsAgBiBr double perovskite solar cells through gallium substitution.

Lead-free halide double perovskite (LFHDP) CsAgBiBr 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 CsAgBiBr solar cells faces challenges due to their wide bandgap (). As a viable strategy to settle this problem, we consider optimization of the optical and photovoltaic properties of CsAgBiBr by Gallium (Ga) substitution. The synthesized CsAgGaBiBr 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 , leading to improvement of the light absorption within the visible spectrum. Importantly, the CsAgGaBiBr solar cell exhibits enhanced performance, as evidenced by higher values of open circuit voltage (), short-circuit current (), and fill factor (FF), which are 0.94 V, 6.01 mA cm, 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 CsAgGaBiBr to be established as a high-performance material for photovoltaic applications. Overall, our development contributes to the advancement of environmentally friendly solar technologies.