Lead-free double perovskite solar cells with PANI passivation Cs2AgBiBr6: reducing bandgap for enhanced photovoltaic performance

This study examines the role of polyaniline (PANI) as a surface passivation material in enhancing the performance of lead-free Cs₂AgBiBr₆-based halide double perovskite solar cells (LFHDPs). A structural analysis using X-ray diffraction (XRD) confirms a cubic crystalline form, with a PANI integration increasing the crystallinity and enlarging the grain size from 26 to 31 nm. The expansion in inter-planar spacing is linked to an improved interfacial charge transport. Optical assessments reveal a lowered bandgap energy (E_g) from 1.88 to 1.85 eV, alongside a substantial increase in charge carrier lifetime from 2.95 to 19.5 ns with the PANI incorporation. The current density–voltage (J-V) demonstrates a superior photovoltaic performance, including a short-circuit current density (J_sc) of 5.1 mA·cm⁻², an open-circuit voltage (V_oc) of 0.90 V, and a power conversion efficiency (PCE) of 3.3%. Devices’ combination Cs₂AgBiBr₆/PANI/Spiro-OMeTAD show a robust humidity resistance, maintaining performance after 10 min of exposure, unlike their PANI-free device, while also exhibiting sustained PCE stability. These advancements stem from suppressed non-radiative recombination, expanded grain dimensions, and effective passivation of grain boundaries. The results position Cs₂AgBiBr₆/PANI composites as viable pathways for eco-friendly, high-stability perovskite solar cells with a competitive efficiency.