The temperature dependences of the photoluminescence (PL) spectra of N, N'-dioctyl-3,4,9,10-perylenedi-carboximide (PTCDI-C-8)/Quaterrylene (QT) heteromolecular thin film and neat-PTCDI-C-8 thin film were investigated to elucidate the effects of a heteromolecular interface on exciton relaxation and recombination processes. The PL spectra were deconvoluted into six components related to Frenkel, two charge-transfer (CT), and excimer exciton states. With the heteromolecular thin film, we found the behavior of the CT excitons to be intriguingly different in terms of luminous efficiency and temperature dependence from that of the Frenkel exciton. In this Letter, we provide detailed analyses of the exciton relaxation and recombination processes at a heteromolecular interface. (C) 2011 Elsevier B. V. All rights reserved.