Facile low-energy and high-yield synthesis of stable α-CsPbI3 perovskite quantum dots: Decomposition mechanisms and solar cell applications

CsPbI3 perovskite quantum dots (PQDs) are considered promising building blocks for photovoltaic and optoelectronic devices. Although ligand-assisted reprecipitation methods have been developed for low-temperature and open-air synthesis of various PQDs, the resulting CsPbI3 PQDs are easily decomposed during purification with non-solvents. Herein, we report a facile low-energy and high-yield synthetic route to produce stable α-CsPbI3 PQDs, which includes a pre-centrifugation step to eliminate the undesirable residues without using any non-solvent. After pre-centrifugation and separation from the residues, the CsPbI3 PQDs in the supernatant can be safely washed twice with a typical non-solvent. To understand the adverse effects of the residues, the decomposition mechanisms of the PQDs are studied in depth by combinatorial analysis of crystallinity, surface reactions, and desorption energy calculations on the (100), (110), and (111) facets. As a result, unreacted Cs+ ions and oleic acids in the precipitated residues are found to induce desorption of surface constituents and undesired phase transitions. The facile low-energy synthesis can be scaled-up to 1 L of crude solution, facilitating preparation of dense PQD solutions. CsPbI3 PQD-based solar cells fabricated through layer-by-layer coating with the dense solution exhibit a power conversion efficiency of 8.28 %.