Donor–Acceptor–Donor “Hot Exciton” Triads for High Reverse Intersystem Crossing in OLEDs

Abstract

Scheme 1. Library of donors and acceptors. Dotted lines denote the bonding positions for D-A-D combinations.

Enhancing Fast RISC in Hot‐Exciton Thermally Activated Delayed Fluorescence Emitter Through Fused Ring Modification: A Theoretical Insights

“…[15] In traditional TADF, the reverse intersystem crossing rate (RISC) occurs from the first excited low-lying triplet state T 1 to the singlet state S 1 , but in the "hot exciton" mechanism the RISC occurs perhaps not from the low-lying triplet, it also occurs from higher excited triplet states. [16,17] Considerably, in conventional TADF emitter, the mechanism involves the transition from the (S 1 -T 1 ) state which is referred to as "cold exciton". [18] In contrast, the "hot exciton" mechanism follows the conversion from the higher-lying triplet, (T n , n > 2) states and singlet (S m , m > 1) states.…”

Exploiting heterocycle aromaticity to fabricate new hot exciton materials

“…12 Although great progress has been made with newly developed hot exciton materials, the most used materials are the archetype molecules, phenanthroimidazole and naphthothiadiazole derivatives, [11][12][13][14][15][16][17][18][19] while the design and development of new materials still resort to trial and error experimental processes. 12,19,20 Therefore, exploring a new molecular design strategy for rationally designing and developing new hot exciton materials remains a challenging yet fascinating task so far.…”

Pioneering research on blue “hot exciton” polymers and their application in solution-processed organic light-emitting diodes

“…Thus, it is worth noting that the oscillator strength and radiative rate in the S 1 state are comparatively subdued, as evidenced by previous research. [13][14][15][16] Fortunately, as an alternative, a novel mechanism which can also realize 100% IQE via a reverse intersystem crossing (RISC) process from the high-lying triplet (T n ) states (hRISC) to S m states has been explored. 17,18 In contrast with the TADF mechanism, fluorescent molecules with hybridized local and chargetransfer (HLCT) state characters inherently have a large overlap between ''particle'' and ''hole'' in excited states, which undoubtedly amplifies the oscillator strength of the S 1 state.…”