Axial enantiomers with donor-regulated TADF feature for multicolor circularly polarized electroluminescence

This study optimized the TADF feature of axial chiral enantiomers through precise donor engineering,and multicolor CP-TADFwas achieved in the axial chiral framework.Three pairs of axial enantiomers with donor-regulated TADF feature,namely(R/S)-TPCBD,(R/S)-DPCBD,and(R/S)-DPACBD,were synthesized by introducing carbazole donors with different substituents onto biphenyl cyanide acceptors.As the electron-donating ability of donors increases,the emission of these axial enantiomers ranges from 455,476 to 552 nm,their singlet-triplet energy gaps(ΔE_(ST))gradually decrease from 0.30,0.22 to 0.02 e V,accompanied by an increasement in the transition rate(k_(RISC))of RISC process,and the k_(RISC)of DPACBD could reach up to 7.16×10^(5)s^(-1).These axial enantiomers also exhibit mirror-image CD and circularly polarized luminescence(CPL)properties.Moreover,OLEDs based on TPCBD,DPCBD,and DPACBD as emitter were then fabricated,which displayed blue,green,and orange electroluminescence with EQE_(max)of 13.0%,16.4%,and 25.0%,respectively.The results also exhibited a phenomenon of device efficiency increasing with the enhancement of donor abilities.Notably,the CP-OLEDs using(R/S)-TPCBD,(R/S)-DPCBD and(R/S)-DPACBD as emitters displayed intense CPEL signals with g_(EL)values of 3.4×10^(-3)/-4.1×10^(-3),3.2×10^(-3)/-3.1×10^(-3)and2.3×10^(-3)/-2.1×10^(-3),respectively.By convenient molecular engineering of donor regulation in the same molecular skeleton,CP-TADF materials with multicolor CPEL and improved device performance could be conveniently achieved.