Highly luminescent CH3NH3PbBr3 quantum dots with 96.5% photoluminescence quantum yield achieved by synergistic combination of single-crystal precursor and capping ligand optimization

Abstract

Inorganic–organic lead halide perovskite quantum dots (PQDs) are promising for application in a wide range of optoelectronic devices due to their high photoluminescence quantum yield (PLQY), tunable band gap, and narrow emission width. Despite intense research effort being devoted to the synthesis of highly luminescent PQDs, the achievement of defect-mediated low PLQY is still challenging. For PQDs processed by the well-known ligand-assisted reprecipitation technique, defects are inevitably formed on the surface, possibly due to the highly ionic precursor solution containing disordered elemental ions. To overcome this problem, in this work, CH3NH3PbBr3 single crystals with low defect densities were prepared using the inverse temperature crystallization method and were applied as sources for PQDs. Furthermore, capping ligands with different alkyl chain lengths were utilized to reprecipitate uniform and stable PQDs. Through the synergistic effect achieved by the use of the single-crystalline precursor and capping ligand optimization, we achieved a near-unity PLQY of 96.5% and a strong green emission. In addition, the obtained highly luminescent PQDs displayed few metallic Pb surface defects and reduced Stokes shifts that will be beneficial for future device applications.