Enhanced colloidal stability of perovskite quantum dots via split-ligand re-precipitation for efficient bi-functional interlayer in photovoltaic application

Abstract

A split-ligand mediated re-precipitation (Split-LMRP) technique for colloidal perovskite quantum dots (QDs) was designed by separately dissolving rich oleic acid (OA) and amine ligands in the synthesis process. OA was used to control the polarity of the nucleation environment and was simultaneously employed as a stabilizer. The Split-LMRP technique allowed purification via the precipitation of QDs from a colloidal solution. The fabrication process is performed under ambient conditions, and the resulting CH3NH3PbX3 (X=Br, I) QDs exhibited strong photoluminescence (PL) emission with a maximum PL quantum yield of 91.5%. The size of the resulting perovskite QDs is tuned in the range of 2–5nm by varying the ligand concentration and type of halide. We also investigated the charge-transport properties of the synthesized QDs using space-charge-limited current analysis and confirmed stable charge carrier mobility even when the QDs solution was spin-coated on a hydrophilic poly (3,4-ethylenedioxythiophene) polystyrene sulfonate film. Furthermore, the enhanced stability of CH3NH3PbX3 (X=Br, I) QDs improved the power conversion efficiency by the uniform surface passivation of the perovskite active layer which induces efficient exciton generation and charge transport.