Molecular engineering of dendritic luminogens with thermally activated delayed fluorescence and aggregation-induced emission characteristics for efficient solution-processed non-doped OLEDs

Abstract

Endowing thermally activated delayed fluorescence (TADF) emitters with aggregation-induced emission (AIE) characteristics and fine film-forming ability is significant for realizing efficient solution-processed non-doped organic light-emitting diodes (OLEDs). Herein, a class...

Determining the Energy Gap between the S1 and T1 States of Thermally Activated Delayed Fluorescence Molecular Systems Using Transient Fluorescence Spectroscopy

“…Thus, transitions from thermally populated vibrational modes always lead to the onset of absorption at photon energies below E S1 and emission at energies above E S1 . Besides, the E T1 value (0–0 transition energy of T 1 ) has been assessed as the highest-energy threshold onset of low-temperature (77 K) phosphorescence spectra, ,− and the peak maximums of both fluorescence and phosphorescence spectra have been used to evaluate E S1 and E T1 in a few experiments. , Apparently, these methods are far from accurate measurements. Recently, Vandewal et al proposed a simple but efficient strategy to precisely determine E S1 as the crossing point of appropriately normalized absorption and emission spectra .…”

Recent progress in thermally activated delayed fluorescence emitters for nondoped organic light-emitting diodes

“…To improve the solubility of AIDF emitters for solution-processed nondoped OLEDs, Qi et al 89 exploited propeller-like dendritic luminogen 79 by connecting the central triphenylamine (TPA) unit with circumambient AIDF emitter (BP-PXZ derivative) arms. The branched alkyl chains in the Cz unit are beneficial for increasing the free volumes, which are important for improving the film-forming ability and preparing pinhole-free uniform films during the solution process.…”

Aggregation‐induced emission luminogens for organic light‐emitting diodes with a single‐component emitting layer

“…Consequently, nondoped OLEDs employing CzTAZPO as the EML exhibited excellent EL performances with EQE max and CE max values of 12.8% and 29.1 cd A −1 , respectively; more interestingly, the EQE roll‐off was negligible (1.6% at 1000 cd m −2 luminance). Recently, Qi and coworkers [119] tailored a series of AIE‐active TADF emitters, 3DPAC–BPCTPA, 3DMAC–BPCTPA, and 3PXZ–BPCTPA, based on a star‐shaped D–A–D configuration containing phenyl ketone as the acceptor and DMAC, DPAC, or PXZ as the donors. In addition, TPA with propeller structure was introduced as the central core and branched alkyl chains were introduced to increase the free volumes for these dendrimers, which is beneficial to making pinhole‐free uniform films during solution‐processing.…”