Recent Progress in Organic Phototransistors: Semiconductor Materials, Device Structures and Optoelectronic Applications

Abstract

Phototransistors combine light detection and signal amplification functions into a single device and are regarded as one of the most important components for optoelectronic integration. In recent years, organic phototransistors (OPTs) have attracted worldwide interest because of their potential advantages of low cost, light weight, excellent flexibility and broadband detection. In this review, a brief description of the working mechanisms and performance metrics of OPTs is presented. Afterwards, the recent progress of OPTs based on the conventional planar fieldeffect transistor structure is presented. Furthermore, from the perspective of novel device architectures and interface engineering, strategies for improving the performance of OPTs are discussed. Flexible optoelectronic devices based on OPTs for potential application in next-generation wearable and humanfriendly electronics are also highlighted. Finally, an outlook for future research directions and challenges for OPTs is provided.

Organic Single Crystals with High Photoluminescence Quantum Yields Close to 100% and High Mobility for Optoelectronic Devices

“…Three important parameters to evaluate the performance of phototransistors are photosensitivity ( P ), photoresponsivity ( R ), and detectivity ( D *), which can be calculated by Equations (S2), Equation (S3), and Equation (S4) (Supporting Information), respectively. [ 6a ] Under 0.0002 mW cm −2 370 nm wavelength illumination, the similar ultrasensitive UV phototransistors for TPA‐An and TBA‐An achieved ultrahigh photosensitivities 1.03 × 10 3 and 3.45 × 10 4 ; ultrahigh photoresponsivities reached 7.19 × 10 5 and 1.50 × 10 5 A W −1 ; and ultrahigh detectivities reached 1.40 × 10 16 and 1.60 × 10 17 Jones, respectively, which are superior to the most reported UV OPTs. Moreover, the switching behavior of TPA‐An and TBA‐An single‐crystal phototransistors in five cycles under ambient conditions showed good operating stability (Figure 4e,g; Figures S7d and S8d, Supporting Information, in the dark → under 0.0002 mW cm −2 with 370 nm wavelength illumination or in the dark → 0.6320 mW cm −2 white light illumination).…”

“…And this attractive characteristic is the key to overcome the noise in the conventional photodiode readout circuit, because the gate field‐controlled tunable gain mechanism can achieve controllable sensitivity and low noise. [ 6 ] In recent years, some multifunctional organic semiconductors with strong fluorescence emission, high mobility, and light sensitivity have been designed and synthesized, and they have been applied in OPTs to obtain excellent photoresponse properties. In 2015, Hu and co‐workers designed and synthesized 2,6‐diphenylanthracene (DPA), whose crystal exhibited a mobility of up to 34 cm 2 V −1 s −1 and a photoluminescence quantum yield (PLQY) of 41.2%.…”

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

“…to facilitate easier and scalable solution deposition [94]. Processing from solution enables tuning of molecular packing in OSC thin films [3,11,18,20,27,63,77]. Creating a highly ordered and uniform surface is critical for efficient charge transport and high-performance device.…”

“…The active material can take the light directly without the shielding of electrodes as it is the case in photodiodes [2,3,12,18]. Organic phototransistors (OPTs) are optically controllable devices based on organic field-effect transistors (OFETs) [1,7,11,18,21,[24][25][26][27]. OFETs play a crucial role in optoelectronic research due to their organic active layer, three-electrode device structure, signal amplifying properties, low noise medium and low voltage operation depending on the dielectric type.…”

“…Table 2 comprehensively presents figures-of-merit of OPT devices. Phototransistor merits of performance[5,11,27].…”