Photosensitivity of top gate C60 based OFETs: Potential applications for high efficiency organic photodetector

•Photoinduced charge transfer across the interface of C60 and parylene.•Organic photodetector with high responsivity.•Photoinduced threshold voltage shift.•Parylene deposition and formation of free radicals.

The comparison of light-induced effects in bottom-gate and top-gate organic field effect transistors (OFETs) provide a clear indication, that the nature of interface between the active layer and the gate dielectric plays a major role in the observed light-induced threshold voltage shift. The nature of interface was also analyzed by electron spin resonance (ESR) experiments, which provides a direct evidence for the creation of free radical species when parylene is deposited on the top of the C60 semiconductor layer. The rate of change of light-induced threshold voltage shift strongly depends on the wavelength and intensity of the incident light, and transverse electric field at the interface. The observed effects provide a strong base for the realization of high efficiency organic photodetectors and optical memory devices. The responsivity of organic photodetector was measured up to 1047 A/W.

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