Green‐Sensitive Phototransistor Based on Solution‐Processed 2D n‐Type Organic Single Crystal

Abstract

Importantly, the ultralow thickness of a 2D organic semiconductor is essential for high-performance phototransistors as it warrants higher charge carrier mobility and faster photoresponse time based on the efficient charge injection and short interlayer recombination distance for trapped charge carriers, respectively. [10,13] In order to develop color-filter-free photodetectors and image sensors, wavelength-selective organic semiconductors in red, green, and blue have been widely investigated, but none of them are based on the crystalline 2D organic semiconductors. [14][15][16][17][18][19] In other words, to the best of our knowledge, 2D organic phototransistors showing green-sensitive absorption for hybrid CMOS image sensor application are yet to be developed. Recently, however, some nonvisible wavelength-selective organic 2D phototransistors have been reported, which respond to either ultraviolet (UV) or near-infrared (NIR) irradiation. Liu et al. reported hybrid phototransistors by growing a few mono layers of dioctylbenzothienobenzothiophene (C8-BTBT) as a UV absorbing layer on a charge-transporting graphene layer by the chemical vapor deposition method. [10] Due to the high charge carrier mobility of graphene and efficient charge separation property of the monolayer of C8-BTBT, they achieved responsivity of 1.57 × 10 4 A W −1 and ultrafast response time of 25 ms under 355 nm laser irradiation. Cao et al. also reported UV absorbing 2D organic phototransistors based on 1,4-bis(4methylstyryl)benzene (p-MSB) by a drop casting method. [12] They found that the internal photoresponsivity of the 2D phototransistors was as high as 2.13 × 10 5 A W −1 under 365 nm light irradiation, which was about two to three orders higher than that of bulk crystals. Wang et al. prepared a few monolayers thick NIR absorbing furan-thiophene quinoidal compound (TFT-CN) by the solution epitaxy method. [11] After transferring the TFT-CN 2D crystal from the water surface to the SiO 2 /Si wafer, they successfully demonstrated high-performing NIR phototransistors with responsivity of up to 9 × 10 4 A W −1 and very low dark current of 0.3 pA under 808 nm laser irradiation. Such high-performance demonstrations in UV and NIR organic 2D phototransistors strongly suggest that 2D phototransistors could be an excellent platform for the full-color CMOS image sensors, specifically for the green-selective 2D organic phototransistors for stacked CMOS architectures. Recently, scientific interests in 2D organic semiconductors have been rapidly growing, and a few review papers are already available. [20,21] In order to establish a design strategy for green-sensitive 2D materials, we examined the structure-property relationship 2D single crystals of down to two-monolayer thickness are fabricated from a push-pull structure-based green light absorbing organic n-type semiconductor, (2E,2′E)-3,3′-(2,5-difluoro-1,4-phenylene)bis(2-(5-(4-(trifluoromethyl) phenyl)thiophen-2-yl)acrylonitrile) (2F-4-TFPTA). The 2F-4-TFPTA 2D single crystal exhibits field-effect el...

Two-Dimensional Field-Effect Transistor Sensors: The Road toward Commercialization

“…Copyright 2021 Wiley-VCH GmbH. (e) Adapted with permission from ref . Copyright 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

“…Over the past decade, a vast number of publications reported diverse methods for synthesizing 2D materials, which include top-down fabrication (e.g., mechanical/liquid exfoliation and gold-mediated exfoliation , ), bottom-up synthesis methods (e.g., physical vapor deposition, solution phase synthesis methods, , chemical vapor deposition (CVD), atomic layer deposition, and molecular beam epitaxy , ), assembly strategies (e.g., floating-coffee-ring driven assembly and dynamic-template-assisted meniscus-guided coating , ), and others. , Figure compares these approaches with five qualitative parameters, including cost, quality, repeatability, scale, and ease of processing. Among these methods, mechanical exfoliation is reported to produce almost defect-free 2D materials with the highest quality. , However, the standard mechanical exfoliation process can only produce relatively small 2D flakes in a large amount of time. , To this end, researchers have tried to develop simple and effective ways of preparing large-area 2D materials with high quality. ,, Liquid phase exfoliation (LPE), one top-down technology similar to mechanical exfoliation, is used to obtain monolayer or few-layer nanomaterials from their bulk crystals.…”

“…Synthesis. Over the past decade, a vast number of publications reported diverse methods for synthesizing 2D materials, which include top-down fabrication (e.g., mechanical/liquid exfoliation 54 and gold-mediated exfoliation 84,164 ), bottom-up synthesis methods (e.g., physical vapor deposition, 165 solution phase synthesis methods, 166,167 chemical vapor deposition (CVD), 168 atomic layer deposition, 60 and molecular beam epitaxy 169,170 ), assembly strategies (e.g., floating-coffee-ring driven assembly 171 and dynamic-templateassisted meniscus-guided coating 163,172 ), and others. 160,173 Figure 3 compares these approaches with five qualitative parameters, including cost, quality, repeatability, scale, and ease of processing.…”

Evolutionary 2D organic crystals for optoelectronic transistors and neuromorphic computing

“…2D OSs with well-defined interfaces and precisely adjusted thicknesses have various of potential for physical implementation of phototransistors because their tunable energy gap can cover a large spectrum range from near-infrared to ultraviolet [53,54,[130][131][132][133]. Low photogating efficiency, low carrier mobility, and short photo-induced exciton diffusion distance in bulk organic materials, on the other hand, impede the development of highly efficient and fast response phototransistors [134][135][136][137].…”

Ultrafast and Stable Organic Single‐Crystal Vertical Phototransistor for Self‐Powered Photodetection and High‐Speed Imaging

“…[5,6] Up to now, a large number of lateral-channel phototransistors based on organic single crystals have been reported. [7][8][9][10] However, high-speed organic phototransistor with high responsivity is still scarce, which is mainly limited by the finite polaron size Organic semiconductor crystals herald new opportunities for fabricating highperformance optoelectronic devices, due to their intrinsic properties including outstanding charge transport properties, long exciton lifetime, and diffusion length. Despite remarkable progress in key figures of merit, the cut-off frequency and responsivity are still lagging behind for most currently reported organic devices.…”