Graphene Sandwich Stable Perovskite Quantum-Dots Light Emissive Ultrasensitive and Ultrafast Broadband Vertical Phototransistors

The dual-functional devices, which can simultaneously detect light and emit light, have a tremendous appeal for multiple applications, including display, sensors, defense, and high-speed optical communication. Despite the tremendous efforts of scientists, the progress of integration of phototransistor, where the built-in electric field separates the photogenerated excitons, and light-emitting diode (LED), where the radiative recombination can be enhanced by band offset, into a single device remains a challenge. Combining the superior properties of perovskite quantum dots (PQDs) and graphene, here we report a light-emissive, ultrasensitive, ultrafast, and broadband vertical phototransistor, which can simultaneously act as an efficient photodetector and light emitter within a single device. The estimated value of external quantum efficiency (EQE) of the vertical phototransistor is ~ 1.2×10¹⁰% and photoresponsivity > 10⁹ AW^-1 with response time of < 50 µs, which exceed all the presently reported vertical phototransistor devices. We also demonstrate that the modulation of the Dirac point of graphene efficiently tunes both amplitude and polarity of the photocurrent. The device exhibits a green emission having a quantum efficiency of 5.6%.