Flexible and Air‐Stable Near‐Infrared Sensors Based on Solution‐Processed Inorganic–Organic Hybrid Phototransistors

Abstract

Flexible and air-stable phototransistors are highly demanded for wearable nearinfrared (NIR) image sensors. However, advanced NIR sensors via low-cost, solution-based processes remained a challenge. Herein, high-performance inorganic-organic hybrid phototransistors are achieved based on solution processed n-type metal oxide/polymer semiconductor heterostructures of In 2 O 3 /poly{5,5′-bis[3,5-bis(thienyl)phenyl]-2,2′-bithiophene-3ethylesterthiophene]} (PTPBT-ET). The In 2 O 3 /PTPBT-ET hybrid phototransistor combines the advantages of both fast electron transport in In 2 O 3 and high photoresponse in PTPBT-ET, showing high saturation mobility of 7.1 cm 2 V −1 s −1 and large current on/off ratio of >10 7 . As a result, the phototransistor exhibits high performance towards NIR light sensing with a responsivity of 200 A W −1 , a specific detectivity of 1.2 × 10 13 Jones, and fast photoresponse with rise/ fall time of 5/120 ms. Remarkably, the hybrid phototransistor, without any passivation, demonstrates excellent electrical stability without performance degradation even after 160 days in air. A 10 × 10 phototransistor array is also enabled by virtue of the high device uniformity. Lastly, flexible In 2 O 3 /PTPBT-ET phototransistor on polyimide substrate is attained, exhibiting outstanding mechanical flexibility up to 1000 bending/releasing cycles at a bending radius of 5 mm. These achievements pave the way for constructing air-stable hybrid phototransistors for flexible NIR image sensor applications.

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

“…It indicated that this novel OPT design could provide durability response to mechanical bending. In another study, a hybrid active layer was utilised to obtain a flexible NIR light-sensitive solution-processed OPT [41]. The hybrid layer was compromised of n-type metal oxide (In 2 O 3 )/polymer {5,5bis[3,5-bis(thienyl)phenyl]-2,2 -bithiophene-3-ethylesterthiophene]} (PTPBT-ET) in a BGTC structure.…”

“…Ongoing research is undertaken to elucidate how to improve charge carrier mobility and detection range of OSCs. However, some existing drawbacks and challenges in realisation of fully solution-processed OFET and OPT, from scientific and engineering perspective, should be contemplated [41]. A device can suffer from poor morphology and/or weak carrier mobility of polymeric semiconductor materials [2,11].…”

“…This is critical in terms of the lifetime of sensor devices [12,43]. Today, uncertainty remains on how to obtain exemplary fully solution-processed, flexible, and long-term stable OFETs and photodetectors [41]. Extensive work is yet to be done to address the shortcomings in realisation and mass production of commercial products of fully solution-processed electronic and optoelectronic devices for practical applications.…”

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

“…It indicated that this novel OPT design could provide durability response to mechanical bending. In another study, a hybrid active layer was utilised to obtain a flexible NIR light-sensitive solution-processed OPT [41]. The hybrid layer was compromised of n-type metal oxide (In2O3) / polymer {5,5'-bis[3,5-bis(thienyl)phenyl]-2,2'-bithiophene-3-ethylesterthiophene]} (PTPBT-ET) in a BGTC structure.…”

Self-assembled peptides-modified flexible field-effect transistors for tyrosinase detection

“…Also, the channel conductance can be modulated by conformational changes after receptors recognition or depended on alterations in surrounding environmental charges when exposure to target molecules ( Bay et al., 2019 ). In addition, flexible and biocompatible bio-FETs could provide a new platform for continuously monitoring individuals' health in a wearable and continuous way, attracting widespread attention in recent years ( Gao et al., 2016 ; Bariya et al., 2020 ; Tai et al., 2018 ; Li et al., 2020 , 2021 ; Kim et al., 2020a ). However, wearable bio-FETs capable of detecting early-stage melanoma remained a challenge ( Emaminejad et al., 2017 ; Koh et al., 2016 ; Lee et al., 2016 ).…”