High Performance Ternary Organic Phototransistors with Photoresponse up to 2600 nm at Room Temperature

Abstract

Infrared (IR) photodetection is important for light communications, military, agriculture, and related fields. Organic transistors are investigated as photodetectors. However, due to their large band gap, most organic transistors can only respond to ultraviolet and visible light. Here high performance IR phototransistors with ternary semiconductors of organic donor/acceptor complex and semiconducting single‐walled carbon nanotubes (SWCNTs), without deep cooling requirements are developed. Due to both the ultralow intermolecular electronic transition energy of the complex and charge transport properties of SWCNTs, the phototransistor realizes broadband photodetection with photoresponse up to 2600 nm. Moreover, it exhibits outstanding performance under 2000 nm light with photoresponsivity of 2.75 × 106 A W−1, detectivity of 3.12 × 1014 Jones, external quantum efficiency over 108%, and high Iphoto/Idark ratio of 6.8 × 105. The device exhibits decent photoresponse to IR light even under ultra‐weak light intensity of 100 nW cm−2. The response of the phototransistor to blackbody irradiation is demonstrated, which is rarely reported for organic phototransistors. Interestingly, under visible light, the device can also be employed as synaptic devices, and important basic functions are realized. This strategy provides a new guide for developing high performance IR optoelectronics based on organic transistors.

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

“…For example, Yang et al reported an IR sensor comprising a charge transfer complex of poly(3,3’’’‐dialkylquaterthiophene) (PQT‐12) and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F 4 ‐TCNQ) in which single‐walled carbon nanotubes (SWCNTs) were used as p‐type channels. [ 145 ] The device architecture and chemical structures of the constituent materials are shown in Figure 9d. Benefiting from the ultralow electronic transition energy of the charge transfer complex between PQT and F 4 ‐TCNQ, the phototransistor achieved broadband photodetection spanning the range of 400−2600 nm, and the resulting device exhibited an ultrahigh photoresponsivity of 2.8 × 10 6 A W −1 and a photodetectivity of 3 × 10 14 Jones under illumination by 2000 nm light with an intensity of 45 μW cm −2 (Figure 9e,f).…”

“…Photoresponses of the photodetector to different wavelengths of light at e) 45 μW cm À2 and at f ) 1 μW cm À2 . Reproduced with permission [145]. Copyright 2021, Wiley-VCH.…”

Recent Progress in 2D Inorganic/Organic Charge Transfer Heterojunction Photodetectors

“…Yang et al fabricated ternary singlewalled carbon nanotubes (SWCNT) photodetector consisting of PQT-12:F4TCNQ (bandgap of 0.4 eV) (Figure 9d,e). [64] In this kind of device, type-II band alignment forms between CT and channel to promote exciton dissociation. Under ultraweak power light illumination (100 nW cm −2 ), channel can still collect signals covering 2600 nm with a detectivity of 3.12 × 10 14 Jones and responsivity up to 2.75 × 10 6 A W −1 (Figure 9f).…”

“…Reproduced with permission. [62][63][64] Copyright 2020, Wiley-VCH; Copyright 2021, Nature Publishing Group; Copyright 2021, Wiley-VCH. CT with Localized Fields.…”

“…Copyright 2020, Wiley-VCH. d) The device architecture of MWCNTs/PQT-12:F4TCNQ phototransistor [64]. e) The absorption spectrum of CTC PQT-12:F4TCNQ [64].…”