Abstract
Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density (JD) and noise current (in). This is commonly accomplished using charge-blocking layers to reduce charge injection. By analyzing the temperature dependence of JD for lead-tin based PPDs with different bandgaps and electron-blocking layers (EBL), we demonstrate that while EBLs eliminate electron injection, they facilitate undesired thermal charge generation at the EBL-perovskite interface. The interfacial energy offset between the EBL and the perovskite determines the magnitude and activation energy of JD. By increasing this offset we realized a PPD with ultralow JD and in of 5 × 10−8 mA cm−2 and 2 × 10−14 A Hz−1/2, respectively, and wavelength sensitivity up to 1050 nm, establishing a new design principle to maximize detectivity in perovskite photodiodes.
Highlights
Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing
The device is built on a glass substrate with a patterned indium tin oxide (ITO) electrode that is covered with the electron-blocking layers (EBL), for which we first use poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)
For several narrow- and mid-bandgap PPDs, the experimental JD exceeds by many orders of magnitude the intrinsic theoretical value J0, excluding thermal charge generation in the bulk of the perovskite as the main cause of JD in absence of injection currents
Summary
Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. To date Pb and mixed Pb–Sn-based perovskite photodiodes (PPDs) have suffered from relatively high dark currents This unwanted property has been attributed to the susceptibility of divalent Sn to oxidation[18], charge injection from the contacts as well as structural and compositional imperfections in the material, leading to pinholes, trap states, and grain boundary leakage[19]. These factors increase JD and the device noise current level (in) limiting the specific detectivity (D*), a key figure of merit that describes the smallest detectable signal. Significant efforts have been devoted to minimizing the dark current in thin film perovskite photodiodes
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