Unconventional Photovoltaic Effect in a Perovskite-Coated Metal–Insulator–Graphene Photodiode

The photovoltaic effect offers a simple way for converting light into an electrical signal. Here, we report on the observation of a zero-bias photocurrent in the forward direction of a perovskite-covered metal-insulator-graphene diode (MIG-diode), which is the opposite current direction compared to conventional photovoltaic cells and photodiodes. Photocurrent mapping has been performed to gain insights into the precise position of photocurrent generation, demonstrating that the zero-bias photocurrent is primarily generated at the edges of the active device area. Using the band structure diagram at the device edge and on the device area, the unconventional photocurrent direction could be well explained. In addition, the key parameters for the MIG-perovskite photodiode were extracted experimentally. This includes the power-dependent responsivity of up to 10 mA/W as well as the noise equivalent power of 2.23 × 10^-13 W/√Hz at zero-bias voltage.