Recent Applications of Interfacial Exciplex as Ideal Host of Power-Efficient OLEDs

Abstract

Currently, exploring the applications of intermolecular donor-acceptor exciplex couple as host of OLEDs with phosphorescence, thermally activated delayed fluorescence (TADF) or fluorescence emitter as dopant is a hot topic. Compared to other host strategies, interfacial exciplex has the advantage in various aspects, such as barrier-free charge injection, unimpeded charge transport, and the energy-saving direct exciton formation process at the “Well”-like heterojunction interface region. Most importantly, due to a very fast and efficient reverse intersystem-crossing (RISC) process, such a host is capable of regulating singlet/triplet exciton populations in itself as well as in the dopant emitters both under photoluminescent (PL) and electroluminescent (EL) driving conditions. In this mini-review, we briefly summarize and comment on recent applications of this ideal host in OLEDs (including both thermal-evaporation OLEDs and solution-processed OLEDs) with diverse emitters, e.g., fluorescence, phosphorescence, delayed fluorescence, or others. Special attention is given to illustrate the peculiar achievement of high overall EL performance with superiorities of low driving voltages, slow roll-off rate, high power efficiencies and satisfied device lifetime using this host strategy, which is then concluded by personal perspectives on the relevant next-step in this field.

Non-toxic near-infrared light-emitting diodes

“…More recently, exciplex-forming hosts have also been proposed to achieve barrier-free charge injection, unimpeded charge transport, and more generally as a cost-effective method as exciplexes can be simply formed by physical blending ( Zhang and Xie, 2019 ). Huang et al demonstrated efficient NIR EL by exploiting the energy transfer between the exciplex-forming host blend and the fluorescent guest ( Huang et al., 2020 ).…”

Recent advances in thermally activated delayed fluorescence for white OLEDs applications

“…The RISC process can accomplish efficiently through smaller ΔE ST . Owing to the preponderances of low turnon voltage and higher power efficiency, there are more and more reports on TADF exciplex-based WOLEDs recently [125][126][127][128][129][130][131][132].…”

Dendritic Interfacial Exciplex Hosts for Solution‐Processed TADF‐OLEDs with Power Efficiency Approaching 100 lm W−1

“…[ 30 ] However, we note that there are few examples of solution‐processed TADF‐OLEDs based on exciplex hosts simultaneously exhibiting low driving voltage and high EQE for achieving high PE. [ 11,31 ]…”