2,2′-Bipyridine-4,4′-dicarboxylic Acid-Mediated Surface Engineering of Mn-Doped CsPbCl3 Perovskite Nanocrystals

Abstract

The metal doping strategy reduces the defect/trap states and improves the stability of CsPbCl3, which is beneficial for optoelectronic applications. Mn doping in CsPbCl3 perovskite nanocrystals (PNCs) has shown an improved photoluminescence quantum yield (PLQY) and stability; however, the emission in these PNCs is limited to trap-mediated energy transfer. Herein, we have demonstrated for the first time improvement in the energy transfer properties, relative PLQY, and stability of Mn-doped CsPbCl3 PNCs by post-synthesis surface passivation with a small organic molecule, 2,2′-bipyridine-4,4′-dicarboxylic acid (BPY). BPY is used as an efficient passivating additive, which reduces surface defects in Mn-doped CsPbCl3 via the electrostatic interactions of carboxyl groups and pyridine nitrogen with less coordinated Pb atoms; hence, the improvement happened in the energy transfers from CsPbCl3 to Mn2+ dopants and the relative PLQY. The relative PLQY of the Mn-doped CsPbCl3 PNCs increased from 23 to 70% after post-synthesis BPY treatment. The Mn-doped CsPbCl3 PNCs were characterized before and after BPY passivation using various characterization techniques. Thermal and photostability studies under ambient conditions and UV light irradiation showed that the BPY-passivated Mn-doped CsPbCl3 PNCs are more stable than the unpassivated ones.