Leflunomide: A versatile additive for defect reduction, enhanced optoelectronic properties and environmental stability of perovskite films

The development of perovskite photoelectric devices with excellent performance is largely dependent on the defects in the perovskite films. To address this issue, a specific drug, leflunomide (LF, C₁₂H₉F₃N₂O₂), was incorporated into the perovskite to reduce defects and improve its photoelectric properties. It is believed that the C=O bond on LF molecule can interact with the uncoordinated Pb²⁺ of the perovskite, thereby reducing non-radiative recombination. This novel approach of incorporating LF into perovskite films has the potential to revolutionize the development of high-performance perovskite photoelectric devices. The trifluoromethyl functional (–CF₃) group on LF can form a protective layer on the surface of the perovskite film, shielding it from water erosion. Moreover, LF can be utilized to alter the nucleation position of perovskite, thus minimizing the number of defects and optimizing the film quality. Consequently, the LF-doped perovskite film displays low trap density and high photoelectric performance. The LF-doped perovskite film showed a trap density of 8.28 × 10¹¹, which is notably lower than the 2.04 × 10¹² of the perovskite film without LF. The responsivity and detectivity of the LF-doped perovskite photodetector were 0.771 A/W and 2.81 × 10¹¹ Jones, respectively, which are much higher than the 0.23 A/W and 1.06 × 10¹⁰ Jones of the LF-undoped perovskite photodetector. Meanwhile, the LF-doped photodetector maintained an initial photocurrent of 86% after 30 days of storage in air, indicating drastically increased environmental stability. This strongly suggests that LF is an effective additive for perovskites utilized in optoelectronic devices with high performance.