Shortwave Infrared Photodetection with oCVD Polythiophene

Abstract

Shortwave infrared (SWIR, λ = 1–3 µm) photodetectors typically use compound semiconductors that are fabricated using high‐temperature epitaxial growth and require active cooling. New technologies that overcome these constraints are the focus of intensive current research. Herein, oxidative chemical vapor deposition (oCVD) is used for the first time to create a room temperature, vapor‐phase deposited SWIR photoconductive detector with a unique tangled wire film morphology that detects nW‐level photons emitted from a 500 °C cavity blackbody radiator—a rarity for polymer systems. A new, window‐based process that greatly simplifies device fabrication is used to construct doped polythiophene‐based SWIR sensors. The detectors feature an 8.97 kΩ dark resistance and are limited by 1/f noise. They feature an external quantum efficiency (gain‐external quantum efficiency) product of 395% and have a measured specific detectivity (D*) of 106 Jones, with the potential to reach D* = 1010 Jones after 1/f noise is minimized. Still, the measured D* is only a factor of 102 lower than a typical microbolometer and after optimization, the newly described oCVD polymer‐based IR detectors will be in a category competitive with commercially available, room temperature lead salt photoconductors and within reach of room temperature photodiodes.

Ultrasensitive Room Temperature Infrared Photodetection Using a Narrow Bandgap Conjugated Polymer

“…Beyond 3 µm, the photocurrent is affected by readout noise of the ηG detection system, producing artificial local maxima that are not present for samples with a higher efficiency measured using the same setup. [ 39 ]…”