The absorption, emission and film structure of co-evaporated mixed film of Chlorogallium phthalocyanine and N,N'-Bis(neopentyl)-3,4,9,10-perylenebis(dicarboximide) are reported. Forster type energy transfer from the BNPTCD to the ClGaPc molecule leads to a considerable enhancement of the phthalocyanine emission in the near infrared. Film structure and molecular organization in the mixed film are studied using transmission and reflection-absorption infrared spectroscopy and atomic force microscopy. A clear correlation between molecular organization and emission properties is established. The spectroscopic and topographical data show that thermal annealing of the mixed films increases phase separation that results in a reduction of the energy transfer efficiency and light emission.