We used the photoexcited TiO2 films to initiate the copolymerization of 3,4-ethylenedioxythiophene with pyrrole, aiming to develop an organic/inorganic heterojunction. Specular reflection infrared spectroscopy analysis was used to monitor the process of polymerization and indicated that the copolymers directly grew on the TiO2 substrate. Dissecting the copolymers with ultraviolet photoelectron spectroscopy revealed the evolution of the valence-band electronic structures. Moreover, the resulting copolymer/TiO2 heterojunctions were investigated using electrochemical impedence and X-ray photoelectron spectroscopy. The Al/poly(3,4-ethylenedioxythiophene-co-pyrrole)/TiO2/ITO heterojunction device that was prepared from the hybrid film exhibited a conspicuous rectification. The heterojunction device was also explored with respect to the conduction models.