A High‐Performance Solution‐Processed Organic Photodetector for Near‐Infrared Sensing

Abstract

Sensitive detection of near-infrared (NIR) light enables many important applications in both research and industry. Current organic photodetectors suffer from low NIR sensitivity typically due to early absorption cutoff, low responsivity and/or large dark/noise current under bias. Herein, organic photodetectors based on a novel ultranarrow bandgap non-fullerene acceptor, CO1-4Cl, are presented, showcasing a remarkable responsivity over 0.5 A W-1 in the NIR spectral region (920-960 nm), which is the highest amongst organic photodiodes. By effectively delaying the onset of the space charge limited current and suppressing the shunt leakage current, the optimized devices show a large specific detectivity around 10 12 Jones for NIR spectral region up to 1010 nm, close to that of a commercial Si photodiode. The presented photodetectors can also be integrated in photoplethysmography for real-time heart rate monitoring, suggesting its potential for practical applications. Near-infrared (NIR) light usually corresponds to the region of electromagnetic radiation with wavelength spanning from about 750 nm to 1400 nm. [1] Despite being invisible to human visual perception, NIR sensing finds applications in a variety of technologies, including medical monitoring, [2] quality inspection, [3] machine vision, [4] and bio-imaging. [5] NIR sensing has been conventionally realized with detectors based on single-crystal inorganic semiconductor materials (e.g. Si, Ge, GaInAs), which typically have drawbacks including costly processing, mechanical inflexibility, and sensitivity to temperature. [6-8] Owing to the low cost, solution processing, material tunability, unique structure-property relationships and good mechanical flexibility, organic semiconductors emerged as an exciting candidate for integrated electronics, lighting, solar cells and photodetection. Particularly, photodetectors based on organic semiconductors have witnessed increasing research endeavor, Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))

The Bulk Heterojunction in Organic Photovoltaic, Photodetector, and Photocatalytic Applications

“…OPDs based on CO1-4Cl have been recently used for heartrate monitoring, due to its NIR spectral response of up to 920-960 nm, with a large D* of around 10 12 Jones, at wavelengths of up to 1010 nm (Figure 7a,b). [231] A P3HT:O-IDTBR-based Figure 7. a) Photograph of the heart rate setup using the OPD.…”

Recent Progress on Broadband Organic Photodetectors and their Applications

“…It is known that the J d of OPDs can be reduced by increasing the thickness of active layer due to the increased R sh , which was verified experimentally by Wu and co-workers. [64] Recently, Huang et al reported PD-OPDs with broadband spectral response of 400 to 1100 nm based on an ultralow-bandgap nonfullerene acceptor CO1-4Cl blended with poly [4,8- [65] The PD-OPDs with a thin active layer (active layer thickness ≈ 87 nm) and a thick active layer (active layer thickness ≈ 300 nm) were fabricated as a comparison to study the J d of PD-OPDs with varied active layer thickness. The J d is efficiently suppressed in the thick PD-OPDs, while the J L is still maintained at reverse bias, as shown in Figure 2d.…”

On Charge Carrier Density in Organic Solar Cells Obtained via Capacitance Spectroscopy

“…In the recent years, new alternatives to classical inorganic semiconductors have garnered a lot of attention. A plethora of applications have been reported based on organic and organicinorganic hybrid semiconductors, among others light emitting diodes, [1,2] field effect transistors, [3][4][5] solar cells, [6,7] energy harvesting devices, [8] photodiodes, [9,10] sensors, and wearable electronics. [11] For the continued improvement of these materials and the devices based on them an important first step is to obtain the density of free charge carriers n, also commonly known as charge carrier density.…”