Photomemory and Pulse Monitoring Featured Solution‐Processed Near‐Infrared Graphene/Organic Phototransistor with Detectivity of 2.4 × 10¹³ Jones

Abstract

Emerging graphene/organic phototransistors are eye-catching technologies owing to their unique merits including easy/low-cost fabrication, temperature independent, and achieving various functions. However, their development in the near-infrared (NIR) region is experiencing a bottleneck of inferior sensitivity due to low exciton dissociation efficiency and inefficient charge extraction rate. Here, a novel-design solution-processed graphene/organic NIR phototransistor is reported, that is, creatively introducing electron extraction layer of ZnO on graphene channel and employing organic ternary bulk heterojunction as photosensitive layer, successfully breaking that bottleneck. The phototransistor exhibits a high responsivity of 6.1 × 10 6 A W −1 , a superior detectivity of 2.4 × 10 13 Jones, and a remarkable minimum detection power of 1.75 nW cm −2 under 850 nm radiation. Considering its excellent NIR detection performance, a noncontact transmission-type pulse monitoring is carried out with no external circuit support, from which human pulse signal and heart rate can be displayed in real time. The phototransistor, interestingly, can be switched into a photomemory function with a retention time of 1000 s in the atmosphere through a gate voltage of −20 V. The design takes the characteristics of graphene/organic phototransistors to a higher level, beyond the limit of sensitivity, and opens up a novel approach for developing multifunction devices.

Recent Advances in Organic Phototransistors: Nonvolatile Memory, Artificial Synapses, and Photodetectors

“…Notably, phototransistor-based near-infrared detectors can be used in a wide range of emerging applications including noninvasive bioimaging, wearable health monitoring, and biometric authentication owing to their mechanical flexibility, affordability, and solution processability. [134][135][136] The material systems used in phototransistor-based photodetectors comprise 1) semiconductors and 2) photoabsorbers, which determine, respectively, the charge transport polarity and photoresponse of the phototransistor. It is possible to combine these two functionalities into a single semiconducting polymer material or molecule for use in a photodetector.…”

“…Notably, phototransistor‐based near‐infrared detectors can be used in a wide range of emerging applications including noninvasive bioimaging, wearable health monitoring, and biometric authentication owing to their mechanical flexibility, affordability, and solution processability. [ 134–136 ]…”

A Review on Solution-Processed Organic Phototransistors and Their Recent Developments

“…Low dimensional materials including quantum dots [158], nanowires [159], 2D materials [160] are reported to offer solutions for high photoconductive gain or tunable Fermi level [161]. A novel design, solution-processed graphene/organic phototransistor was reported by He et al for a NIR region detection [162]. They realised a multifunctional device that could work both as a pulse monitoring and a photomemory.…”

High-Performance Near-Infrared Photodetectors Based on the Synergy Effect of Short Wavelength Light Filter and Long Wavelength Response of a Perovskite/Polymer Hybrid Structure

“…Near-infrared (NIR) light, due to its low attenuation and large penetration depth in the medium, has spawned various applications in optical communications, biomedical testing, environmental monitoring, and other fields. − Highly efficient and sensitive detection of NIR light has become a very important content in the development of near-infrared applications. The traditional way to detect NIR light specifically utilizes an inorganic wideband photodetector combined with an external visible light filter to eliminate the visible light interference .…”