Enhancement of efficiency and stability of 3D/2D hybrid perovskite solar cells with ionic liquid additive

Perovskite solar cells (PSCs) have revolutionized photovoltaic technologies with their high power conversion efficiency (PCE) and low production costs. However, their long-term stability and environmental resistance remain significant challenges for commercial viability. This study investigates how ionic liquid (IL) additives can improve the efficiency and stability of PSCs. In this study, the effect of 1-butyl-4-methylpyridinium tetrafluoroborate (BMPyBF₄) ionic liquid on the photovoltaic performance and stability of 3D/2D hybrid PSCs is explored. Different concentrations of BMPyBF₄ were incorporated into the Cs₀.₀₅(FA₀.₉MA₀.₁)₀.₉₅Pb(I₀.₉Br₀.₁)₃ composition to optimize the device performance. Structural and electronic properties were examined using XRD, Pole-Figure, GIWAXS, SEM, AFM, KPFM, XPS, UPS, ToF-SIMS, PL, and TRPL analyses. DFT calculations revealed that BMPyBF₄ forms strong interactions with the perovskite surface, facilitating defect passivation and reducing charge transport barriers. The J-V, IPCE, EIS, and Mott-Schottky measurements were conducted to evaluate device performance and charge transport dynamics. At the optimum BMPyBF₄ concentration (0.5% mmol), the device exhibited a 1.18 V open-circuit voltage (VOC), 24.37 mA/cm² short-circuit current density (JSC), 82% fill factor (FF), and a maximum PCE of 23.6%. According to ISOS protocols, operational stability tests showed that the reference device lost 33% of its initial efficiency after 500 hours, whereas the 0.5% BMPyBF₄-incorporated devices retained 99% of their initial efficiency after 1000 hours. Furthermore, in thermal stability tests conducted at 65 °C, the reference device exhibited a 59% loss in 100 hours, while the BMPyBF₄-incorporated device showed only 38% degradation in 200 hours. These results demonstrate that BMPyBF₄ enhances charge transport dynamics by providing defect passivation and reducing recombination losses. This study reveals that charge transport dynamics in PSCs can be optimized through additive engineering and that ionic liquid additives play a crucial role in this process.