Alkyl ammonium iodide-based ligand exchange strategy for high-efficiency organic-cation perovskite quantum dot solar cells

Whereas lead halide perovskite-based colloidal quantum dots (PQDs) have emerged as a promising photoactive material for solar cells, the research to this point has predominantly focused on inorganic cation PQDs despite the fact that organic cation PQDs have more favourable bandgaps. In this work, we develop solar cells using narrow bandgap organic cation-based PQDs and demonstrate substantially higher efficiency compared with their inorganic counterparts. We employ an alkyl ammonium iodide-based ligand exchange strategy, which proves to be substantially more efficient in replacing the long-chain oleyl ligands than conventional methyl acetate-based ligand exchange while stabilizing the α phase of organic PQDs in ambient conditions. We show a solar cell with the organic cation PQDs with high certified quasi-steady-state efficiency of 18.1% with 1,200-h stability under illumination at open-circuit conditions and 300-h stability at 80 °C.