The integration of perovskite photodetectors with thin-film transistor (TFT) backplane or complementary metaloxide-semiconductor CMOS circuit is a key step towards prototyping perovskite-based image sensors. Here, we demonstrate a pixel configuration for indirect X-ray detection comprising of IGZO TFTs and perovskite photodiodes (PDs). The perovskite photodiode is patterned by a two-step deposition method. Our integrated TFT/PD pixel shows a weak light detection capability down to 4 nW cm-2 , and a fast-transient response to the pulse light and gate switching. Combining with a CsI scintillator, the integrated pixel achieves a specific X-ray sensitivity of 8.2 10 2 μC mGyair-1 cm-3. Theoretically, with a stateof-the-art scintillator, the new pixel can provide a detectable signal for X-ray imaging at a dose rate as low as 10 μGyair s-1. This work provides an advanced pixel design for high resolution, high sensitivity, and high frame-rate flat-panel imager.
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 (V oc ) ∼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/cm 2 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 photovoltagecoupled DG−TFT provides a strategy for developing sensitive and low-power image sensors.
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