Creation of efficient solution-processed OLEDs via a strategy of the host-guest system constructing with two small cross-linkable TADF molecules

Based on the strategy of using small cross-linkable thermally activated delayed fluorescence (TADF) molecules act as the host or the guest, a highly efficient TADF polymer is successfully constructed to develop efficient solution-processed organic light-emitting diodes (OLEDs). In this paper, two small cross-linkable TADF monomers, namely DV-2CzBN and DV-2CzTBN, are designed and synthesized. Simultaneously, small molecular TADF monomers are linked together using two vinylbenzyl linkers to form polymers. Systematic studies demonstrate that the polymers based on the host-guest TADF system can maintain the intrinsic TADF nature unchanged, and also effectively inhibit the triplet excitons quenching. Encouragingly a solution-processed OLED based on the host-guest system TADF polymer showed an excellent device performance with the maximum current efficiency (CE) of 25.1 cd A−1, the power efficiency (PE) of 19.6 lm W−1 and external quantum efficiency (EQE) of 11.4%, respectively, which are two times higher in device efficiency than the corresponding device with the polymers based on the single-molecule system.