Aggregation induced intermolecular charge transfer in simple nonconjugated donor–acceptor system

Abstract

The exploration of exciplex for organic light-emitting diodes (OLEDs) has been fleetly developed. However, many of them confront with the problems like phase separation and poor solubility, hampering their utilization in solution process. Hence, a series of soluble exciplex luminophores with the simple architecture of D-spacer-A (mCP-6C-TRZ, phCz-6C-TRZ and 2phCz-6C-TRZ) are synthesized and characterized, in which, the alkyl chain as ample spacer breaks the molecular backbone conjugation, induces intermolecular charge transfer process instead of intramolecular charge transfer in solid state. These materials are endowed with narrowed singlet−triplet splitting energy (ΔE ST ), efficient reverse intersystem crossing (RISC) process, and distinct thermally activated delayed fluorescence (TADF) characteristics. In view of their high triplet energy level (E T ) and bipolar carrier transport ability, where efficient exciplexes are applied as the host, the solution-processed phosphorescence devices realize a low efficiency roll-off of 7.0% at 1000 cd m −2 , high luminance, current efficiency (CE) and external quantum efficiency (EQE) of 25,990 cd m −2 , 20.0 cd A −1 and 6.7%, respectively. These results offer a promising tactic to the establishment of exciplex with TADF feature as host for fabricating efficient solution processed OLEDs. Three exciplex materials with D-spacer-A configuration, were synthesized and characterized, where the long alkyl chain as spacer provided a platform for intermolecular charge transfer instead of intramolecular charge transfer, induced TADF characteristic, as well as the better EL performance of doped solution processed OLEDs obtained based on mCP-6C-TRZ as bipolar host. • Simple exciplex hosts with spacer linker, were synthesized and characterized. • The alkyl chain as spacer deters intra-CT, induces inter-CT and distinct TADF trait. • The solution-processed OLED based on mCP-6C-TRZ realized a low roll-off. • A luminance of 25,990 cd m −2 , CE and EQE of 20.0 cd A −1 and 6.7%, were also realized.