Solution Processed Metal-Oxide:Polymer Interlayer Improves Perovskite Photodetector Response Speed, Dark Current, and Stability

Abstract

Metal halide perovskites (MHP) are a promising class of solution processable materials for visible and near-infrared imaging, combining performances nearing commercial silicon detectors with a simpler processing. However, MHP photodiodes may suffer from poor stability, while challenges on the thickness and uniformity of the interlayers used complicate deposition and reproducibility, often requiring the use of thermal evaporation. Here, we introduce a solution processable mixed electron transport layer (ETL) composed of zinc oxide (ZnO) nanoparticles blended with Poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN). This hybrid interlayer combines the advantages of both metal oxide and organic transport layers, enabling fast, low-noise MHP photodiodes with promising stability and improved reproducibility. The mixed interlayer enables dark currents of 2.1 × 10^-8 A cm^-2 at -1 V bias, a white background noise below 6.5 × 10^-14 A Hz^-1/2 at -0.1 V, and an apparent specific detectivity of about 10¹² Jones in the visible range. The device achieves a cutoff frequency (f_-3dB) of 2.1 MHz for an area of 1.51 mm², limited by its series resistance and capacitance, with further improvements possible through area reduction. Moreover, the ZnO:PFN interlayer enhances device shelf-life stability, maintaining nearly unchanged dark current over 570 days of aging. This work demonstrates the potential of mixed metal oxide-polymer interlayers for advancing MHP photodiodes toward practical, high-performance applications.