Hot exciplexes in U-shaped TADF molecules with emission from locally excited states

Abstract

Fast emission and high color purity are essential characteristics of modern opto-electronic devices, such as organic light emitting diodes (OLEDs). These properties are currently not met by the latest generation of thermally activated delayed fluorescence (TADF) emitters. Here, we present an approach, called “hot exciplexes” that enables access to both attributes at the same time. Hot exciplexes are produced by coupling facing donor and acceptor moieties to an anthracene bridge, yielding an exciplex with large T1 to T2 spacing. The hot exciplex model is investigated using optical spectroscopy and quantum chemical simulations. Reverse intersystem crossing is found to occur preferentially from the T3 to the S1 state within only a few nanoseconds. Application and practicality of the model are shown by fabrication of organic light-emitting diodes with up to 32 % hot exciplex contribution and low efficiency roll-off.

Influence of regioisomerism in bis(terpyridine) based exciplexes with delayed fluorescence

“…We therefore conclude that RISC will preferentially occur from T 1 to S 1 as the major pathway; however, depending on the exciplex geometry, there might also be RISC among higher level CT and LE states resembles hot exciton and hot exciplex TADF processes. 42–44 The fact that the lowest-energy 1 CT states of our three isomers are nearly isoenergetic agrees well with their nearly indistinguishable photoluminescence spectra (see Fig. 3c).…”

A Novel Strategy toward Thermally Activated Delayed Fluorescence from a Locally Excited State

“…31 Moreover, the LE-TADF was recently realized in anthracence derivatives with facing donor and acceptor, and the OLED based on the LE-TADF exhibits excellent performance. 32 Therefore, the proposed LE-TADF design strategy would open a new avenue for extending the TADF materials. Boron difluoride derivatives are excellent candidates to explore the luminescence mechanism, which has been widely reported from fluorescence, TADF, and room-temperature phosphorescence (RTP), 33−38 indicating the adjustability of the energy gaps between the low-lying excited states, namely ΔE(S 1 −T 1 ), ΔE(S 1 −T 2 ), and ΔE(T 1 −T 2 ), through the introduction of a heteroatom or groups to the mother structure.…”

Simple Phenazine‐Based Compounds Realizing Superior Multicolored Emission

“…Regardless of which method was used, to achieve high efficiency performance, most compounds either experienced arduously picking of specific subjects (acceptors) that were tedious to synthesize, [21] or were coupled with more and even different donors. [32,33] Meanwhile, even though the interest in TADF materials is shifting to the operational lifetime, [34] color purity, [23] reverse intersystem crossing rate, and so on, [31,[34][35][36] however, according to recent works reported by Ma [37] and Adachi and co-workers, [24,38] new mechanisms about hybrid local and charge-transfer (HLCT)-type TADF have been proposed. We hope that depending on this work, these new mechanisms could be applied to the conventional TADF configuration, further paving the way for the follow-up studies of the mechanisms of TADF.A new family of phenazine-based compounds is synthesized to achieve multicolored emission from deep blue (418 nm) to red (625 nm).…”