Exciplex formation of excited 4-phenylbenzophenone (PBP) triplet with triethylamine (TEA) in organic solution has been studied by steady state and pulse-laser photo-luminescence measurements. Direct evidence for triplet exciplex formation was provided by the observation of emission at longer wavelengths than that of the phosphorescence of PBP. The quenching mechanism is proposed to involve a pi, pi* triplet of PBP to form an exciplex with the ground state of TEA. The difference in the photophysics between (3)(pi, pi*) PBP and (3)(n, pi*) benzophenone (BP) probably plays an important role in the electron-transfer process. (C) 2007 Published by Elsevier B.V.