Single-component white afterglow from dual emission based on carbazole-pyrimidine-benzene derivatives

Achieving single-component organic white afterglow material remains a great challenge owing to the difficulties in simultaneously supporting long-lived emissions from varied excited states and getting complementary emission color. Here, a dual emission model that the radiative decays from singlet and triplet excited states was proposed to afford white afterglow. Based on the constructed carbazole-pyrimidine-benzene (CPB) building block, white afterglow was successfully achieved by CPB-H, CPB-MeO, and CPB-F at room temperature. Especially, CPB-H exhibits white afterglow with a lifetime about 0.3 s. The white afterglow was realized by dual emissions including blue TADF and yellow phosphorescence emission. The dual emissions are mainly dependent on the electronic structures of designed molecules, where the appropriate energy level matching between singlet and triplet states are necessary for ISC process in monomer or stacked dimer and for RISC process in other monomer or dimer.