Photoelectric characterization of thin vacuum deposited diphenyl-diketo-pyrrolopyrroles films

The modern organic semiconductor devices are designed and fabricated as multilayer structures with stacked organic/inorganic thin films. There are strong requirements to the properties of the particular films comprising such structure, e. g. film homogeneity, thickness uniformity and roughness. Physical Vacuum Deposition (PVD) technique fulfils all of these requirements and even has the capability to produce the whole multilayer structure in the same vacuum cycle. Diphenyl-diketo-pyrrolopyrroles (DPP) are low molecular weight materials with promising luminescence and photoelectrical properties. Current paper deals with PVD of thin DPP films and investigation of their photoelectric properties. The organic films and inorganic electrodes of the multilayer structures were prepared in the same vacuum cycle, and then the samples were encapsulated in a glove box without exposure to oxygen. ITO|DPP|Al structures of about 150 nm thicknesses were prepared. The surface morphology of the films was studied by SEM imaging. Photoelectric characterization consisted of spectral sweep of the generated photocurrent, I-V characteristics in dark and under illumination and intensity sweep of the photocurrent for a given wavelength. Photoelectrical properties were successfully demonstrated and directions toward performance improvements have been given.