Plenty of room at the top: exploiting nanowire – polymer synergies in transparent electrodes for infrared imagers

Abstract

Infrared (IR) photodetectors are playing an increasingly central role in modern technology, expanding well beyond their niches in military applications to emerging fields like machine vision and consumer electronics. While colloidal quantum dot (cQD) IR detectors in the near-IR (NIR) to short-wave IR (SWIR) now rival conventional bulk materials in laboratory testing, scaling them up to fully integrated IR imagers, particularly in the mid-wave IR (MWIR) remains a challenge. One roadblock is the limited availability of top electrodes with high IR transparency and low sheet resistances. Here we present a silver nanowire (Ag-NW) – polyvinyl alcohol (PVA) composite that simultaneously addresses both issues. The composite delivers over 70% optical transmittance across the NIR, SWIR and MWIR regions with a low sheet resistance ∼11 Ω sq⁻¹. We demonstrate its integration as a transmissible top contact in a photodiode achieving detectivities ∼2.9 × 10¹¹ Jones at 1800 nm, which is comparable to bottom illuminated IR cQD detectors.