Gate‐Controlled Polarity‐Reversible Photodiodes with Ambipolar 2D Semiconductors.

A photosensor with an amplitude‐tunable and polarity‐reversible response under gate modulation has potential as a computational photosensor, which can provide more recognition degree of data to enhance signal processing efficiency. Although, the ambipolar 2D semiconductors possess unique gate‐tunable properties, the question of how to utilize this property to design polarity‐reversible photodiodes for intelligent applications remains unanswered. Here, gate‐controllable polarity‐reversible photodiodes based on ambipolar 2D semiconductors with an asymmetrically metal‐contacted architecture are proposed. By controlling the gate‐field, the local carrier type and density profile can be manipulated in the channel due to the partial shielding feature of the asymmetrically metal‐contacted architecture, resulting in a polarity‐reversible photodiode. The reported WSe2‐based photodiode possesses excellent rectifying behavior with a rectification ratio over 105, photovoltaic performance with 90% external quantum efficiency, and 2.3% power conversion efficiency under gate regulation. Meanwhile, the device exhibits reversible polarity of photovoltage from a negative to positive state under gate control. By utilizing the reversible photovoltage of the WSe2 photodiode, an optoelectronic switch with a photovoltage polarity signal is demonstrated without a bias voltage. This photovoltage‐reversible homodiode paves the way to develop 2D devices with multiple operation modes for potential applications in high‐efficiency photovoltaics, intelligent vision sensors, and logic optoelectronics. [ABSTRACT FROM AUTHOR]