Multifunctional Conjugated Ligand with Intimate Binding Improves Luminescence, Charge Transport, and Stability in CsPbBr3 Perovskite Nanocrystals

Abstract

Colloidal metal halide perovskite nanocrystals (PNCs) face critical challenges such as poor dispersion stability, ligand desorption, surface defects, and limited charge transport. In this study, a new ligand engineering strategy is introduced using a semiconducting conjugated oligoelectrolyte (COE), QTF2Br, to address these issues in CsPbBr3 PNCs. QTF2Br strongly binds to the PNC surface through bidentate coordination, effectively passivating surface defects and supplying additional bromide ions. This leads to a significantly enhanced photoluminescence quantum yield exceeding 94% and an increase in exciton binding energy from 38.3 to 108.3 meV. Additionally, QTF2Br facilitates F & ouml;rster resonance energy transfer to the PNC core, functioning as an optical antenna that amplifies green emission by 2.2 times compared to conventional oleic acid/oleylamine-treated PNCs (PNC-OA). The QTF2Br-treated PNCs (PNC-QTF2Br) exhibit improved colloidal stability in polar solvents (e.g., tetrahydrofuran) and retain their PL intensity in toluene for over 7 days. Solid-state films show excellent thermal stability, resisting interparticle aggregation and maintaining clear particle definition. Moreover, the semiconducting nature of QTF2Br enhances charge transport between nanocrystals. This COE-based ligand engineering approach offers a promising solution to overcome key limitations of conventional PNCs for advanced optoelectronic applications.