Role of electron withdrawing groups in Phenoxazine-Oxadiazole based D-A molecules towards enriching TADF emission
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Abstract
Herein, we reported the effect of electron withdrawing units such as trifluoromethyl (CF3) and cyanide (CN) substituted in an Thermally activated delayer fluorescent (TADF) molecule 10-(4-(5-Phenyl-1,3,4-oxadiazol-2-yl)phenyl)-10H-phenoxazine (PXZ-OXD). The addition of this electron withdrawing units increased the acceptor strength and it can reduce the interaction between PXZ and OXD that helps to lower the gap between singlet to triplet states of excitons. The Time resolved photoluminescence studies revealed the improved reverse intersystem crossing with high quantum yield for 4’-CNPXZOXD. As a result of this substitution, the emission wavelength moved from blue to green. However, 3-4% increment in external quantum efficiency have been achieved in OLEDs with this substituted TADF materials. The detailed role of this electron withdrawing unit substitution and its effects are delved in detail.