Flexible Broadband Graphene Photodetectors Enhanced by Plasmonic Cu3-xP Colloidal Nanocrystals

The integration of graphene with colloidal quantum dots (QDs) that have tunable light absorption affords new opportunities for optoelectronic applications as such a hybrid system solves the problem of both quantity and mobility of photocarriers. In this work, a hybrid system comprising of monolayer graphene and self-doped colloidal copper phosphide (Cu3-xP) QDs is developed for efficient broadband photodetection. Unlike conventional PbS QDs that are toxic, Cu3-xP QDs are environmental friendly and have plasmonic resonant absorption in near-infrared (NIR) wavelength. The half-covered graphene with Cu3-xP nanocrystals (NCs) behaves as a self-driven p-n junction and shows durable photoresponse in NIR range. A comparison experiment reveals that the surface ligand attached to Cu3-xP NCs plays a key role in determining the charge transfer efficiency from Cu3-xP to graphene. The most efficient three-terminal photodetectors based on graphene-Cu3-xP exhibit broadband photoresponse from 400 to 1550 nm with an ultrahigh responsivity (1.59 x 10(5) A W-1) and high photoconductive gain (6.66 x 10(5)) at visible wavelength (405 nm), and a good responsivity of 9.34 A W-1 at 1550 nm. The demonstration of flexible graphene-Cu3-xP photodetectors operated at NIR wavelengths may find potential applications in optical sensing, biological imaging, and wearable devices.