Printable and Flexible Phototransistors Based on Blend of Organic Semiconductor and Biopolymer

Abstract

Printable and flexible organic phototransistors (OPTs) make comprehensive requirements for the organic semiconductors (OSCs), including high photosensitivity, decent transistor characteristics, appropriate solution viscosity, and good film flexibility. It has been challenging to obtain such semiconductors. Here, we demonstrated that by taking advantage of the interfacial charge effect, printable and flexible OPTs with high performance can be successfully fabricated through simply blending common OSCs with polymers. Using 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene and an insulating biopolymer polylactide, OPTs with blended and layered structure are both fabricated and investigated. The photoresponses of the OPTs can be modulated by gate voltage over 1000 times, and their responsivities are measured up to 400 A W−1. As compared to the layered OPTs, the blended ones exhibit higher photocurrent to dark current ratio (up to 105) and better light detection limit (lower than 0.02 mW cm−2). The improvements are attributed to larger interfacial area and more intensive charge trapping effect. The flexible OPTs are further fabricated by inkjet printing the blended solution. This work presents OPTs with comprehensive advantages including low cost, enhanced photosensitivity, great flexibility, and printability, which are realized by simply blending common OSC with polymer, and thus provide an inspiration for the design of novel organic electronics.

Flexible Photodetectors Based on Novel Functional Materials

“…The superior performance upon bending tests is attributed to the good film stability and contacts between the hybrid film and Ag electrodes. More recently, printable and flexible phototransistors consisting of a blended or layered structure of 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) and an insulating biopolymer polylactide (PLA) hybrid were successfully fabricated (Figure d,e), as reported by Huang and colleagues . The prominent characteristics of C8‐BTBT such as high carrier mobility, excellent stability and solubility, as well as great biocompatibility of the PLA give rise to the formation of hybrid blended film with good uniformity and electrical properties.…”

“…Time‐dependent photoresponse of the device to periodic light pulses f) at flat and g) bended at a radius of 300 µm (light intensity: 1.0 mW cm −2 ). d–g) Reproduced with permission . Copyright 2017, Wiley–VCH.…”

Integration of Biomaterials into Sensors Based on Organic Thin‐Film Transistors

“…Biodegradable PLA and derivatives are commonly employed in biological and medical applications such as drug delivery, medical implants, and tissue engineering. Moreover, they can be incorporated into organic electronics as flexible substrates or dielectric . For example, Bao and Bettinger have fabricated OFETs based on poly ( l ‐lactide‐ co ‐glycolide) (PLGA), whose chemical structure can be found in Figure a .…”

Performance improvement of organic phototransistors by using polystyrene microspheres

“…Organic phototransistors (OPTs) have been intensively studied in recent years owing to the combined advantages of phototransistors and organic semiconductors [1][2][3][4][5][6][7]. Phototransistors, as one type of the photodetectors, possess a gate and a dielectric layer for amplifying the electrical signals and improving the corresponding photosensitive parameters like responsivity and detectivity.…”

“…Dinaphtho[2,3-b:2ʹ,3ʹf]thieno [3, 2-b]thiophene (DNTT) and 2,7-dioctyl [1]benzothieno [3,2-b][1]benzothiophene (C8BTBT) were selected because of their relatively high mobility and stability [29,30]. By incorporating PS microspheres, PS microspheres/DNTT-based phototransistors (PS/DNTT OPTs) enhanced photosensitivity (ratio of photo current to dark current, simplified as I light /I dark ratio) by two orders of magnitude compared with DNTT OPTs.…”