Highly-Sensitive Resonance-Enhanced Organic Photodetectors for Shortwave Infrared Sensing

TL;DR

This paper introduces a simple optical microcavity strategy to significantly enhance the sensitivity and spectral range of organic SWIR photodetectors, achieving record efficiencies and detectivities at longer wavelengths.

Contribution

The study presents a novel microcavity design that extends the detection range of organic photodetectors, surpassing traditional narrow-gap absorber methods.

Findings

Achieved >50% EQE over 450-1100 nm spectrum.

Recorded peak D* of 1.1E13 Jones at 1100 nm.

Demonstrated record EQE of 35% with IR6 at 1150 nm.

Abstract

Shortwave infrared (SWIR) has various applications, including night vision, remote sensing, and medical imaging. SWIR organic photodetectors (OPDs) offer advantages such as flexibility, cost-effectiveness, and tunable properties, however, lower sensitivity and limited spectral coverage compared to inorganic counterparts are major drawbacks. Here, we propose a simple yet effective and widely applicable strategy to extend the wavelength detection range of OPD to a longer wavelength, using resonant optical microcavity. We demonstrate a proof-of-concept in PTB7-Th:COTIC-4F blend system, achieving external quantum efficiency (EQE) > 50 % over a broad spectrum 450 - 1100 nm with a peak specific detectivity (D*) of 1.1E13 Jones at 1100 nm, while cut-off bandwidth, speed, and linearity are preserved. By employing a novel small-molecule acceptor IR6, a record high EQE = 35 % and D* = 4.1E12 Jones are obtained at 1150 nm. This research emphasizes the importance of optical design in optoelectronic devices, presenting a considerably simpler method to expand the photodetection range compared to a traditional approach that involves developing absorbers with narrow optical gaps.