Spiropyran fluorescent indicator for in-situ visual detection of lead leakage in lead-based perovskite solar cells

Lead (Pb)-based perovskite solar cells (PSCs) are promising clean energy systems due to excellent photoelectric conversion efficiency and cost-effective fabrication. However, when the fragile PSCs suffers from imperceptible micro-damage, it often leads to the leakage of Pb^{2 +}, posing a threat to device performance and environmental safety. Therefore, developing technologies capable of swiftly pinpointing leakage areas at the incipient damage stage and enabling timely remediation or replacement measures is crucial for effectively managing Pb²⁺ leakage risks and ensuring long-term operational integrity of equipment. Here, we develop an in-situ visual detection method via spiropyran fluorescent indicator, 1-(2-hydroxyethyl)-3,3-dimethylindolinobenzospiropyran-6′-nitrobenzospiropyran (HDN), for the in-situ early detection of Pb²⁺ leakage in lead-based PSCs. Under 365 nm UV excitation, the closed-ring spiropyran structure of HDN converts to a red-fluorescent merocyanine structure. This structure can selectively recognize Pb²⁺ and undergo complexation reaction with it, resulting in the quenching of red fluorescence. The fluorescence intensity and Pb²⁺ concentration show a linear correlation within a defined range, with a detection limit as low as 0.42 μg cm⁻². To enhance practical applicability, we integrated this detection technology with a WeChat color recognition applet, enabling precise in-situ monitoring of Pb²⁺ leakage in series-type PSCs. Overall, the method provides a new idea for the in-situ visual detection of Pb²⁺ leakage in Pb-based PSCs.