Photovoltage-Coupled Dual-Gate InGaZnO Thin-Film Transistors Operated at the Subthreshold Region for Low-Power Photodetection

Photodetectors with high sensitivity for weak light illumination is highly desirable for large-area image sensors. Here, we introduce a sensor pixel design that integrates a perovskite photodiode (PD) with a dual-gate InGaZnO thin-film transistor (DG–TFT). In our pixel configuration, the light intensity-dependent photovoltage of the perovskite PD directly adjusts the gate field of the DG–TFT, then the optical signal is converted into a photovoltage signal and gets amplified at the subthreshold region of the DG–TFT. Spin-coated perovskite PD exhibits an open-circuit voltage (Voc) ∼3 times higher than that of the commercial silicon PD under weak light illumination. The capability of detecting weak light with low power consumption is enabled by the coupling of the photovoltage of a perovskite PD to the DG–TFT operated at the subthreshold region. The photovoltage-coupled DG–TFT achieves a light-to-dark current ratio of 26 under 5 μW/cm2 with an operation power as low as 27 pW. The theoretical noise equivalent power of such pixels is estimated to be in the sub-picowatt per square centimeter range. The integrated photovoltage-coupled DG–TFT provides a strategy for developing sensitive and low-power image sensors.