Controlling Band gap of Triphenylamine-Based Conjugated Polymers for Efficient Blue Quantum Dot Light Emitting Diodes: Effects of Electron-Withdrawing Groups
발표자
()
초록
내용
Optimization of the energy level alignment between quantum dot (QD)-based emitting layers (EMLs) and hole transporting layers (HTLs) is critical for improving charge balance. The low valence band level of blue QDs can induce large energy barrier at the HTL/EML interface, resulting in the suppression of the hole injection from HTLs to EMLs. Here, electron-withdrawing group-substituted triphenylamine-based polymers are developed to minimize the energy offset between HTLs and EMLs. The inclusion of electron-withdrawing groups successfully leads to downshifting of the HOMO levels, with little effect on the lowest unoccupied molecular orbital (LUMO) levels, as analyzed by cyclic voltammetry (CV) and UV–vis absorption measurements. In addition, the charge mobility measurement using the space charge-limited current (SCLC) method reveals that the HTLs consisting of the triphenylamine-based derivatives have similar hole mobilities. We expect that the newly designed polymers can enhance the efficiencies of blue QD-LEDs.