Thermally Activated Delayed Fluorescent Gain Materials: Harvesting Triplet Excitons for Lasing

Abstract

Thermally activated delayed fluorescent (TADF) materials have attracted increasing attention because of their ability to harvest triplet excitons via a reverse intersystem crossing process. TADF gain materials that can recycle triplet excitons for stimulated emission are considered for solving the triplet accumulation problem in electrically pumped organic solid-state lasers (OSSLs). In this mini review, recent progress in TADF gain materials is summarized, and design principles are extracted from existing reports. The construction methods of resonators based on TADF gain materials are also introduced, and the challenges and perspectives for the future development of TADF gain materials are presented. It is hoped that this review will aid the advances in TADF gain materials and thus promote the development of electrically pumped OSSLs.

Advances in Energy‐Level Systems of Organic Lasers

“…Moreover, the triplet-singlet annihilation would further reduce the stimulated emission density in the case of electrically pumping. [102][103][104] Thence, improving the utilization efficiency of triplet populations is critical for the realization high-gain organic lasers. Fu et al first achieved triplet-phosphorescence organic laser by introducing sulfur substitution and intramolecular charge transfer (ICT) interaction in metal-free pure organic fluorescent molecules.…”

A very low lasing threshold of DABNA derivatives with DFB structures

“…27,28 However, there are few examples of TADF materials showing lasing behaviour because their excited states generally have a charge transfer (CT) character owing to the connection of the donor-acceptor structures, which show a rather slow radiative decay rate. [29][30][31][32][33][34][35] In addition, their thresholds are all significantly higher than 1 mJ cm À2 , 36 which needs to be decreased to the level of fluorescent materials for practical applications.…”

Double boron-embedded multiresonant thermally activated delayed fluorescent materials for organic light-emitting diodes

“…This MR effect-suppressed vibronic coupling leads to a narrow full width at half maximum (FWHM), and the rigid molecular structure helps realize a minimal Stokes shift below 30 nm, resulting in a low reorganization energy and high photoluminescence quantum yield (PLQY) [39][40][41][42][43][44] . Notably, compared to conventional TADF emitters, the MR-TADF emitters have significant advantages such as high color purity (high PLQY) and narrow emission spectra with FWHM of ~30 nm 35,38,39,[45][46][47] . As of now, many groups developed over 100 molecules in MR-TADF emitters.…”