Spectrum-tunable graphene hybrid photosensor

Abstract

The fundamental properties of graphene have been intensively investigated in recent years for its unique optical, electrical, mechanical and thermal conducting properties. In particular, its zero-bandgap structure and broad spectrum absorption make graphene a promising application candidate in the field of photodetection. Nevertheless, two major inherent deficiencies of graphene inhibit its comprehensive application in photodetectors: single-layer graphene has a low light absorption rate of 2.3% only, and graphene has an ultra-short photo-excited carrier lifetime τlifetime. The introduction of organic dyes provides an effective solution to these drawbacks under the synergy of the photovoltaic effect and photogating effect taking place in the Schottky junction at the graphene-TiO2-dye interface. Herein, we successfully fabricated a spectrum-tunable graphene photosensor with photoresponsivity as high as 8.8×104 A/W thanks to the ultra-high mobility of graphene and light absorption efficiency of organic dyes. Spectrum-tunable photoresponse enables graphene photosensors decorated with different organic dyes to exhibit a distinct absorption spectrum which is essential for a full-color image sensor. The photocurrent generated in the photodetector is proportional to the incident optical power and reaches a saturation plateau when the light intensity is over 0.1 μW. To develop an integrated, spectrum-tunable, full-color gamut photosensor for color imaging, we did a tentative test to scale up the photosensor array with 1 μm thick Parylene thin film, the spectral response test demonstrated inducing Parylene C would not significantly affect the photoresponsivity and absorption spectrum while providing a physically and chemically stable encapsulation.