Miniaturized VIS‐NIR Spectrometers Based on Narrowband and Tunable Transmission Cavity Organic Photodetectors with Ultrahigh Specific Detectivity above 10¹⁴ Jones

Abstract

Spectroscopic photodetection plays a key role in many emerging applications such as context‐aware optical sensing, wearable biometric monitoring, and biomedical imaging. Photodetectors based on organic semiconductors open many new possibilities in this field. However, ease of processing, tailorable optoelectronic properties, and sensitivity for faint light are still significant challenges. Here, the authors report a novel concept for a tunable spectral detector by combining an innovative transmission cavity structure with organic absorbers to yield narrowband organic photodetection in the wavelength range of 400–1100 nm, fabricated in a full‐vacuum process. Benefiting from this strategy, one of the best performed narrowband organic photodetectors is achieved with a finely wavelength‐selective photoresponse (full‐width‐at‐half‐maximum of ≈40 nm), ultrahigh specific detectivity above 1014 Jones, the maximum response speed of 555 kHz, and a large dynamic range up to 168 dB. Particularly, an array of transmission cavity organic photodetectors is monolithically integrated on a small substrate to showcase a miniaturized spectrometer application, and a true proof‐of‐concept transmission spectrum measurement is successfully demonstrated. The excellent performance, the simple device fabrication as well as the possibility of high integration of this new concept challenge state‐of‐the‐art low‐noise silicon photodetectors and will mature the spectroscopic photodetection into technological realities.

Near‐Infrared Materials: The Turning Point of Organic Photovoltaics

“…Since the NIR light has a longer propagation distance with a low attenuation in the biological tissues, OPDs have presented great potential in environmental monitoring, medical examinations, nighttime surveillance, and wearable electronics. [183][184][185][186] Nguyen and co-workers reported a novel organic photodetector based on a ultranarrow-bandgap acceptor, CO1-4Cl (Figure 13a). [187] The organic photodetectors had a responsivity over 0.5 A W −1 in the wavelength region from 920 to 960 nm.…”

Infrared Organic Photodetectors Employing Ultralow Bandgap Polymer and Non‐Fullerene Acceptors for Biometric Monitoring

“…Organic electronic technology involving carbon-based semiconductor materials has many desirable features compared to its inorganic counterpart including roomtemperature processing from solution and reduced manufacturing costs while delivering large areas of lightweight, flexible devices with strong light absorption and optical and electronic tuneability. [3][4][5][6][7] Emerging designs for biological imaging operate within the second (NIR-II: 1000-1300 nm) and third (NIR-III: 1550-1870 nm) biological windows, which offer deeper tissue penetration, improved image contrast, and reduced photobleaching. [1,8,9] This makes organic devices that can detect those spectral regions while delivering conformal coverage, biocompatibility, and lack of cooling requirements, a preferred choice for wearable health monitors.…”

“…Organic electronic technology involving carbon‐based semiconductor materials has many desirable features compared to its inorganic counterpart including room‐temperature processing from solution and reduced manufacturing costs while delivering large areas of lightweight, flexible devices with strong light absorption and optical and electronic tuneability. [ 3 – 7 ]…”

Photomultiplication‐Type Organic Photodetectors for Near‐Infrared Sensing with High and Bias‐Independent Specific Detectivity

“…The description is reproduced here for completeness. [ 45 ] All OPDs investigated in this work are constructed by a thermal evaporation vacuum system with a base pressure of less than 10 −7 mbar. Before deposition, ITO substrates (Thin Film Devices Inc., USA) are cleaned for 15 min in different ultrasonic baths with NMP solvent, deionized water, and ethanol, followed by O 2 plasma for 10 min.…”