Organic field-effect transistors (OFETs) have emerged as promising sensors targeting chemical analytes in vapors and liquids. However, the direct detection of solid chemicals by OFETs has not been achieved. Here for the first time, we describe the direct detection of solid chemical analytes by organic electronics. An organic diode structure based on a horizontal side-by-side p–n junction was adopted and shown to be superior to OFETs for this purpose. The diodes showed more than 40% current decrease upon exposure to 1 ppm melamine powders. The estimated detection limit to melamine can potentially reach the ppb range. This is the first demonstration of an electronic signal from an interaction between a solid and an organic p–n junction directly, which suggests that our lateral organic diodes are excellent platforms for the development of future sensors when direct detection of solid chemicals is needed. The approach developed here is general and can be extended to chemical sensors targeting various analytes, opening unprecedented opportunities for the development of low-cost and high-performance solid chemical sensors.

A facile strategy was designed for the in situ synthesis of MoS2 nanospheres on functionalized graphene nanoplates (MoS2@f-graphene) for use as lithium-ion battery anode materials. A modified Birch reduction was used to exfoliate graphite into few-layer graphene followed by modification with functional groups. Compared to the most common approach of mixing MoS2 and reduced graphene oxide, our approach provides a way to circumvent the harsh oxidation and destruction of the carbon basal planes. In this process, alkylcarboxyl functional groups on the functionalized graphene (f-graphene) serve as sites where MoS2 nanospheres crystallize, and thus create bridges between the MoS2 nanospheres and the graphene layers to effectively facilitate electronic transport and to avoid both the aggregation of MoS2 and the restacking of graphene. As anode materials, this unique MoS2@f-graphene heterostructure has a high specific capacity of 1173 mAh g–1 at a current density of 100 mA g–1 and a good rate capacity (910 mAh g–1 at 1600 mA g–1).Keywords: composites; functionalized graphene; heterostructure; lithium-ion battery anode; modification; molybdenum disulfide;

AbstractAll-inorganic lead halide perovskite quantum dots (IHP QDs) have great potentials in photodetectors. However, the photoresponsivity is limited by the low charge transport efficiency of the IHP QD layers. High-performance phototransistors based on IHP QDs hybridized with organic semiconductors (OSCs) are developed. The smooth surface of IHP QD layers ensures ordered packing of the OSC molecules above them. The OSCs significantly improve the transportation of the photoexcited charges, and the gate effect of the transistor structure significantly enhances the photoresponsivity while simultaneously maintaining high Iphoto/Idark ratio. The devices exhibit outstanding optoelectronic properties in terms of photoresponsivity (1.7 × 104 A W−1), detectivity (2.0 × 1014 Jones), external quantum efficiency (67000%), Iphoto/Idark ratio (8.1 × 104), and stability (100 d in air). The overall performances of our devices are superior to state-of-the-art IHP photodetectors. The strategy utilized here is general and can be easily applied to many other perovskite photodetectors.

AbstractPolymer dielectrics in organic field-effect transistors (OFETs) are essential to provide the devices with overall flexibility, stretchability, and printability and simultaneously introduce charge interaction on the interface with organic semiconductors (OSCs). The interfacial effect between various polymer dielectrics and OSCs significantly and intricately influences device performance. However, understanding of this effect is limited because the interface is buried and the interfacial charge interaction is difficult to stimulate and characterize. Here, this challenge is overcome by utilizing illumination to stimulate the interfacial effect in various OFETs and to characterize the responses of the effect by measuring photoinduced changes of the OFETs performances. This systemic investigation reveals the mechanism of the intricate interfacial effect in detail, and mathematically explains how the photosensitive OFETs characteristics are determined by parameters including polar group of the polymer dielectric and the OSC side chain. By utilizing this mechanism, performance of organic electronics can be precisely controlled and optimized. OFETs with strong interfacial effect can also show a signal additivity caused by repeated light pulses, which is applicable for photostimulated synapse emulator. Therefore, this work enlightens a detailed understanding on the interface effect and provides novel strategies for optimizing OFET photosensory performances.

Organic field-effect transistors (OFETs) offer great potential applications in chemical and biological sensing for homeland security, environmental monitoring, industry manufacturing, and medical/biological detection. Many studies concentrate on sensitivity and selectivity improvement of OFET-based sensors. We report four organic semiconductors with different alkyl side chain lengths but the same π-conjugated core structure for OFETs. Our work focuses on the molecular structure of organic semiconductors (OSCs). Alkyl side chains can hinder the diffusion of ammonia into the OSCs layer, which blocks the interaction between ammonia and conducting channel. The result also reveals the relationship between the alky chain and the film thickness in sensitivity control. These results are expected to be a guide to the molecular design of organic semiconductors and the choice of OSCs.有机场效应晶体管在化学和生物传感、国土安全、环境监测、工业生产、医疗生物检测中具有很大的应用前景.如何提高基于有 机场效应晶体管传感器的灵敏度和选择性的研究已有很多报导. 本文用四种具有不同长度的烷基侧链和相同π–π共轭结构的有机半导体 来制备有机场效应晶体管, 集中研究有机半导体的分子结构. 烷基侧链可以减缓氨气在有机半导体层中的扩散, 阻止氨气和导电通道之间 的相互作用. 研究结果揭示了改变烷基侧链长度和薄膜厚度可以调控传感器的灵敏度, 这些结果有助于指导有机半导体材料的分子设计 和种类选择.

Excellent electrical properties and large-scale fabrication are essential for extending the application of flexible organic electronics in practice. Organic semiconductor materials usually suffer from low charge carrier mobility, while carbon-based materials, such as graphene and carbon nanotubes (CNTs), often exhibit a rather low on/off ratio. Incorporating carbon-based materials into organic field-effect transistors (OFETs) is expected to combine their advantages. However, the dispersity of CNTs in organic semiconductors is rather poor, leading to a limited development of the hybrid devices. In this work, we overcame the challenge by subtly utilizing the advantages of covalently functionalized double-walled carbon nanotubes (f-DWCNTs). The f-DWCNTs can be well dispersed in solutions of organic semiconductor with a wide concentration range, which also makes the hybrid devices solution processable. OFETs based on f-DWCNT and an organic semiconductor hybrid exhibited higher source-drain currents as compared with that based on an organic semiconductor only. In addition, the threshold voltage of the OFETs decreased obviously due to charge injection enhancement by the f-DWCNTs. The comprehensive electric performance of the hybrid OFETs were further optimized by adjusting the mixing ratio of the two materials. Therefore, we demonstrated that incorporating f-DWCNTs into organic semiconductors is a simple and effective route to enhance the electric performance of solution-processed OFETs, and this strategy is expected to further advance flexible organic electronics for practical applications.

Disinfection byproducts (DBPs) in drinking water, resulting from water disinfecting processes, are harmful to human health even at very low concentrations. It has been challenging to simultaneously realize low-cost, portable, rapid and highly sensitive DBPs detection. Here, we report miniaturized electronic sensors for detecting trace amounts of analytes in water, which are fabricated with covalently modified double-walled carbon nanotubes (DWCNTs). The sensors presented ultrahigh sensitivity to halogenated DBPs, and exhibited a detecting level for dibromoacetic acid (DBAA), a typical halogenated DBPs, of lower than 1 part per trillion (10−12 w/v). The selectivity of the sensors can be tuned by adjusting the functional groups modified on the outer wall of the DWCNTs. The sensor based on amino group-modified DWCNTs showed a selective response to halogenated DBPs. Real-time detection has been further demonstrated by using the device integrated with a microfluidic channel, and the sensor showed a rapid and sensitive response to 10 parts per billion DBAA in aqueous elution. Therefore, this work not only achieved portable, rapid and simple water quality monitoring in daily life, but also, by taking advantage of unique chemical diversity and bilayer structure of functionalized DWCNTs, provided a promising sensor platform especially for trace amount of analytes in solutions.

Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX3 perovskite materials with a generalized formula of (RNH3)2(CH3NH3)n−1MnX3n+1, and adopt the Ruddlesden–Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (C4H9NH3)2PbI4 (n = 1, one-layered perovskite), (C4H9NH3)2(CH3NH3)Pb2I7 (n = 2, two-layered perovskite) and (C4H9NH3)2(CH3NH3)2Pb3I10 (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, Ilight/Idark ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.Keywords: high sensitivity; layer-structured perovskites; lead iodide; photodetector; sensor

Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport.Keywords: charge mobility; organic field-effect transistor; organic photovoltaics; time-of-flight; transport dynamics; π-conjugated small molecules;

CH3NH3PbI3 perovskite-based optoelectronics have attracted intense research interests recently because of their easy fabrication process and high power conversion efficiency. Herein, we report a novel photodetector based on unique CH3NH3PbI3 perovskite films with island-structured morphology. The light-induced electronic properties of the photodetectors were investigated and compared to those devices based on conventional compact CH3NH3PbI3 films. The island-structured CH3NH3PbI3 photodetectors exhibited a rapid response speed (<50 ms), good stability at a temperature of up to 100 °C, a large photocurrent to dark current ratio (Ilight/Idark > 1 × 104 under an incident light of ∼6.59 mW/cm2, and Ilight/Idark > 1 × 102 under low incident light ∼0.018 mW/cm2), and excellent reproducibility. Especially, the performance of the island-structured devices markedly exceed that of the conventional compact CH3NH3PbI3 thin-film devices. These excellent performances render the island-structured device to be potentially applicable for a wide range of optoelectronics.Keywords: CH3NH3PbI3 perovskites; high sensitivity; island-structured thin film, sensor; photodetector

Disinfection byproducts (DBPs) in drinking water, resulting from water disinfecting processes, are harmful to human health even at very low concentrations. It has been challenging to simultaneously realize low-cost, portable, rapid and highly sensitive DBPs detection. Here, we report miniaturized electronic sensors for detecting trace amounts of analytes in water, which are fabricated with covalently modified double-walled carbon nanotubes (DWCNTs). The sensors presented ultrahigh sensitivity to halogenated DBPs, and exhibited a detecting level for dibromoacetic acid (DBAA), a typical halogenated DBPs, of lower than 1 part per trillion (10−12 w/v). The selectivity of the sensors can be tuned by adjusting the functional groups modified on the outer wall of the DWCNTs. The sensor based on amino group-modified DWCNTs showed a selective response to halogenated DBPs. Real-time detection has been further demonstrated by using the device integrated with a microfluidic channel, and the sensor showed a rapid and sensitive response to 10 parts per billion DBAA in aqueous elution. Therefore, this work not only achieved portable, rapid and simple water quality monitoring in daily life, but also, by taking advantage of unique chemical diversity and bilayer structure of functionalized DWCNTs, provided a promising sensor platform especially for trace amount of analytes in solutions.