A single-layer molecularly doped electroluminescent (OEL) polymer thin film has been prepared via a vapor codeposition process. The presented method may be conveniently applied to many dye-doped polymer thin film systems yet without having to go through existing complicated conventional synthesis and fabrication processes. This method, proven in this work to be feasible experimentally, was executed by simultaneously codepositing an EL active dye, a hole-transporting molecule triphenyldiamine derivative (TPD), and two polyimide thin film forming monomers on an indium-tin oxide (ITO) substrate. Carrier injection was provided from an ITO anode and a thermally evaporated aluminum electrode. Electron-hole recombination and the green light in EL spectra, with an emission maximum at 515 nn, were triggered at a driving voltage of 14 V. Two primary degradation behaviors were identified. First, hydrolysis of the thin films led to the reduction in EL intensity. Second, nonuniform structure formation of the top Al metal in the Al and codeposition film interface caused reduction in the active emission area and increased the driving voltage required.