Excited-state regulated electroluminescence performance from thermally-activated delayed fluorescence (TADF) to hybridized local and charge-transfer (HLCT) emission

Realization of switching between TADF and HLCT emissions through modulation of the intramolecular charge transfer character

“…Recently, Zhou et al 37 reported that TADF and HLCT emissions can be achieved in D–A type molecules containing the acceptor benzophenazine ( DPPZ ) 37 and Tian et al demonstrated that switching between TADF and HLCT emissions can also be realized by choosing popularly used triazine as the acceptor unit and fluorene as the π-bridge. 38 However, both DPPZ - and triazine-based TADF molecules exhibit relatively low photoluminescence quantum yields in doped films (33% and 22%, respectively). Therefore, the molecular design strategy for both highly efficient TADF and HLCT molecules with fixed acceptor units needs to be improved.…”

Benzoxazole-Based Hybridized Local and Charge-Transfer Deep-Blue Emitters for Solution-Processable Organic Light-Emitting Diodes and the In fluences of Hexahydrophthalimido

“…Thus, two compounds can harvest the triplet excitons and convert to singlet excitons through the hot exciton channel from T 4 to S 1 , corresponding to the hot exciton mechanism . Moreover, the BPCPCHY provided a larger SOC constant between the T 4 and S 1 states (ξ­(S 1 , T 4 )) than that of BPCP, which can be ascribed to the carbonyl group of HP units and which is in favor of the faster hRISC process. ,− …”

“…Thus, the benzoxazole-based doped OLEDs were improved through optimization of BPCP and BPCPCHY concentrations doped into mCP host materials. The emitting layer was replaced by 1,3-bis-(carbazol-9-yl)benzene (mCP) doped with different concentrations (10,30,50, and 70 wt %) of BPCP or BPCPCHY. As shown in Figure 10b,c, the BPCP-based devices exhibit a deepblue emission, and the EL spectral peaks are 428, 436, 436, and 436 nm with corresponding CIE coordinates of (0.16, 0.05), (0.16, 0.06), (0.16, 0.07), and (0.16, 0.08), respectively, demonstrating a slight red shift with the doping concentration increasing.…”

Simple excited-state modification toward a deep-blue hybridized local and charge-transfer (HLCT) fluorophore and non-doped organic light-emitting diodes

“…This makes HLCT materials possess more advantages than others in developing non-doped blue materials and OLEDs. Until now, various acceptor moieties including imidazole (benzoimidazole, naphthimidazole, phenanthro [9,10-d] imidazole, and pyrene[4,5-d]imidazole), 22,[27][28][29] thiadiazole (benzothiadiazole and naphthothiadiazole), 23,[30][31][32][33] pyrimidine, 34 triazole, [35][36][37] triazine (tris(triazolo)triazine and 2,4-diphenyl-1,3,5-triazine), 21,38 benzonitrile, 39,40 diphenylsulfone, 41 and benzophenone have been used to construct efficient HLCT emitters. Although blue HLCT-OLEDs with a high external quantum efficiency (EQE) exceeding 10% have been achieved, the reported pure deep-blue HLCT materials and non-doped OLEDs with the CIEy r 0.046 are still rare, 42,43 due to the ICT effect and aggregation induced redshift.…”