Ortho-substituted biphenyl (BP) has been used to improve the RISC process by introducing a LE state in the two-step RISC mechanism without substantially increasing the conjugation in the molecule. The compound 4mCzBN-BP emits from a CT state [E(S1) = 2.80 eV] and has a T1 state of HLCT character [E(T1) = 2.69 eV] in toluene, both of which are energetically close to the triplet LE state of BP (2.95 eV).