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Description
All-inorganic cesium lead iodide (CsPbI₃) perovskite quantum dots (PQDs) have emerged as promising candidates for next-generation photovoltaic and optoelectronic applications owing to their optoelectronic properties and solution processability.
However, the dynamic binding of intrinsic ligands (OA and OAm) to the PQD surface is easily disrupted in the polar environment of the purification process, leading to the formation of abundant surface defects, particularly (VI) and (VA) vacancies. This defect density is further amplified under ambient purification conditions, where moisture and oxygen accelerate phase instability and degrade the optoelectronic properties. Despite extensive efforts to improve the optoelectronic properties and stability of PQDs, effective strategies to suppress the defect formation during ambient purification are still lacking. We aim to develop a robust and scalable surface modification and purification strategy that mitigates surface defect generation under open-air conditions, enabling the production of high-quality PQDs suitable for subsequent formulation into quantum dot inks for large-area perovskite solar cells.
To achieve this, guanidinium trifluoroacetate was introduced during the final cooling stage (120–100 °C) of CsPbI₃ PQD preparation. We find that the surface modification with guanidinium cations effectively controls Ostwald ripening, as observed by in-situ PL measurements that reveal real-time emission peak shifts during cooling to enable insights into suppressed particle growth and ripening dynamics, passivates surface trap states, and enhances phase stability. As a result, the treated CsPbI₃ PQDs exhibit a significantly enhanced photoluminescence quantum yield (~80% relative to ~54% for the control sample), a narrower emission linewidth, and improved structural stability compared with their conventionally purified counterparts.
This work establishes a practical route for the reliable synthesis of high-quality CsPbI₃ PQDs under ambient conditions, offering a scalable strategy for the production of highly stable perovskite QDs. Importantly, these stable PQDs are well-suited for formulation into conductive quantum dot inks, enabling scalable fabrication of large-area perovskite solar cells and other optoelectronic devices.