Luminescent radicals, whose emission comes from the doublet exited state, have potential application in the field of organic optoelectronics. However, few radicals show
luminescence at room temperature. Herein, a new pure red-emissive biphenyl-type (N-pyrido[3,4-b]indolyl)bis(2,4,6-trichlorophenyl)methyl radical (PyID-BTM) is designed and
synthesized, in which the carbazole moiety of CzBTM (a previously reported biphenylmethyl radical by our group) is successfully replaced by β-carboline. Its photophysical
properties, including the ground and excited states, and the radiative and non-radiative processes are systematically investigated. beta carboline
The photoluminescence quantum efficiency (ϕ = 19.5%) of PyID-BTM is ten times higher than that of CzBTM (ϕ = 2.0%) in cyclohexane. The crystal structure, magnetic properties,
photostability and electroluminescence performance of PyID-BTM are studied. An optimized OLED device using PyID-BTM as an emissive dopant showed pure red emission with
CIE coordinates of (0.649,0.317) and a maximum EQE of 2.8%, and the formation ratio of doublet excitons was up to 70%. This study provides a new approach for designing high
-performance luminescence biphenylmethyl radicals for applications in organic electroluminescence.