nz0c00093_si_001.pdf (783.59 kB)
Enhancing Charge Carrier Delocalization in Perovskite Quantum Dot Solids with Energetically Aligned Conjugated Capping Ligands
journal contribution
posted on 2020-02-18, 21:16 authored by Evan T. Vickers, Emily E. Enlow, William G. Delmas, Albert C. DiBenedetto, Ashraful H. Chowdhury, Behzad Bahrami, Benjamin W. Dreskin, Thomas A. Graham, Isaak N. Hernandez, Sue A. Carter, Sayantani Ghosh, Qiquan Qiao, Jin Z. ZhangCompared to bulk
perovskites, charge transport in perovskite quantum
dot (PQD) solids is limited. To address this issue, energetically
aligned capping ligands were used to prepare methylammonium lead bromide
(MAPbBr3) PQDs toward enhancing surface charge carrier
density in PQD solids. Trans-cinnamic acid (TCA) and its derivates,
functionalized with electron-donating or electron-withdrawing groups
to modulate energy levels, are used as passivating exciton-delocalizing
ligands (EDLs) to decrease the energy gap with respect to the PQD
core. 3,3-Diphenylpropylamine (DPPA) ligand is shown to stabilize
EDLs on the PQD surface through π–π stacking intermolecular
interaction, mitigating charge trapping and nonradiative decay. Passivation
using EDLs in combination with DPPA increases the photoluminescence
(PL) quantum yield (QY) (90%), photoconductivity, extraction, mobility,
transport time, and lifetime of charge carriers in PQD solids. Prototype
PQD-based light-emitting diodes (LEDs) were demonstrated with a low
turn-on voltage of 2.5 V.