What question did this study set out to answer?

The central aim is to enhance the performance of organic photodetectors for near-infrared sensing.

May 7, 2026Laser & Photonics Review1 citations

Tunable Near‐Infrared IIa Narrowband Organic Photodetectors Enabled by Microcavity–Charge Transfer State Coupling

HZHanbo ZhuAdvanced Optical Technologies (United States)QXQin XiongNanchang University ZJZiyan JiaJiaxing University

Key Points

The central aim is to enhance the performance of organic photodetectors for near-infrared sensing.
Developed a microcavity‐enhanced organic photodetector using the PTB7‐Th:BTPSeV‐4F system.
Optimized optical thickness for achieving resonance at 1208 nm with specific FWHM and EQE values.
Measured performance metrics including dark current density, detectivity, and noise‐equivalent power across variable cavity lengths.
Achieved a resonance wavelength of 1208 nm with a FWHM of 17 nm and EQE of 10.7%.
Demonstrated a dark current density of 38 nA cm − 2 at 0 V bias and a detectivity of 1.39 × 10 10 Jones.
Enabled clear spectral discrimination of substances like water, ethanol, and propylene glycol.

Abstract

ABSTRACT Organic photodetectors (OPDs) with narrowband response in the near‐infrared (NIR) region are essential for cost‐effective spectroscopic sensing. Here, we report a microcavity‐enhanced OPD based on the PTB7‐Th:BTPSeV‐4F system, where charge transfer (CT) transitions are resonantly amplified by a Fabry–Pérot cavity. By optimizing the optical thickness, the device achieves a first‐order resonance at 1208 nm with a narrow full width at half maximum (FWHM) of 17 nm and an external quantum efficiency (EQE) of 10.7%, compared to ≈1% for the non‐cavity reference. The detector exhibits a low dark current density of 38 nA cm − 2 at 0 V bias, a detectivity of 1.39 × 10 10 Jones, and a noise‐equivalent power (NEP) of 18.75 pW. By tuning the cavity length, the resonance wavelength can be continuously adjusted from 1050 to 1350 nm, covering the biologically relevant NIR‐IIa window and extending beyond the response limit of conventional Si detectors while avoiding costly InGaAs devices. Benefiting from CT state–cavity synergistic enhancement, the device operates in a self‐powered mode and enables clear spectral discrimination of water, ethanol, and propylene glycol. This work establishes an effective strategy for narrowband, low‐noise, deep‐NIR organic photodetection, highlighting the potential of organic materials for compact spectroscopic sensing.

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