Highly reproducible organic field-effect transistor from pseudo 3-dimensional triphenylamine-based amorphous conjugated copolymer

An easily accessible 3D donor-acceptor polymer based on triphenylamine (PTPA-co-DTDPP) is synthesized by a simple and efficient route. Owing to its non-fibrillar structure, PTPA-co-DTDPP features highly reproducible charge carrier mobility of up to 3.3 x 10(-3) cm(2) V(-1) s(-1) at various fabrication conditions.close181

Ambipolar organic field-effect transistors fabricated using a composite of semiconducting polymer and soluble fullerene

Organic field-effect transistors (FETs) with equivalent hole and electron mobilities have been demonstrated. The devices were fabricated using a phase separated mixture of regioregular poly(3-hexylthiophene) and [6,6]-phenyl C-61-butyric acid methyl ester as the active layer and using aluminum (Al) for the source and drain electrodes. Measurements of the source-drain current versus gate voltage gave an electron mobility of mu(e)=2.0x10(-3) cm(2)/V s and hole mobility of mu(h)=1.7x10(-3)cm(2)/V s. The ambipolar FET properties arise from the use of Al electrodes for the source and drain; the contacts between the Al electrodes and the active layer are improved by thermal annealing at elevated temperatures (150 degrees C), thereby enabling balanced injection for both holes and electrons in a single device.open413

Photovoltaic effects on the organic ambipolar field-effect transistors

An organic multifunctional device, which can function as an ambipolar field-effect transistor (FET) and a photovoltaic (PV) cell, has been demonstrated using a phase separated mixture of poly(3-hexylthiophene) and [6,6]-phenyl C-61-butyric acid methyl ester. The gold (Au) electrode used for hole injection in the FET mode (source) acts as the anode in PV cell mode, and the aluminum (Al) electrode for electron injection in the FET mode (drain) acts as the cathode in PV cell mode. The device exhibits clear PV phenomena under illumination at zero gate bias with a power conversion efficiency of 0.6% as well as the properties of an ambipolar FET when the gate bias is applied.open292

Multilayer bipolar field-effect transistors

Field-effect transistors comprising a layer of regioregular poly(3-hexylthiophene) (rr-P3HT) separated from a parallel layer of the soluble fullerene,[6,6]-phenyl C-61-butyric acid methyl ester (PCBM) by a layer of titanium suboxide (TiOx), are fabricated by solution processing. Because the TiOx is an electron transporting material and a hole blocking material, this multilayer architecture operates either in the p-channel mode with holes in the rr-P3HT layer or in the n-channel mode with electrons in the PCBM layer.open201

Carrier generation and transport in bulk heterojunction films processed with 1,8-octanedithiol as a processing additive

Improved performance of polymer-based solar cells based on poly[2,6-(4,4-bis-(2-ethylhexyl)- 4H -cyclopenta[2,1-b;3,4- b???] dithiophene)-alt-4,7-(2,1,3-benzo-thiadiazole)] PCPDTBT has been obtained by using 1,8-octanedithiol (ODT) as a processing additive in the polymer solution used to spin cast the bulk heterojunction films. Although ultrafast spectroscopy studies indicate that the carrier losses are reduced in the films processed with ODT [similar to the reduced carrier losses after thermal annealing of bulk heterojunction (BHJ) materials made from P3HT:PCBM], the magnitude of the reduction is not sufficient to explain the observed factor of 2 increase in the power conversion efficiency. From the analysis of carrier transport in field effect transistors, we find increased electron mobility in the PCPDTBT: PC70 BM composites when fabricated with ODT, which is indicative of enhanced connectivity of PC70 BM networks. The improved electron mobility appears to be the primary origin of the improved power conversion efficiency in BHJ films.open453

High mobility solution-processed hybrid light emitting transistors

We report the design, fabrication, and characterization of high-performance, solution-processed hybrid (inorganic-organic) light emitting transistors (HLETs). The devices employ a high-mobility, solution-processed cadmium sulfide layer as the switching and transport layer, with a conjugated polymer Super Yellow as an emissive material in non-planar source/drain transistor geometry. We demonstrate HLETs with electron mobilities of up to 19.5 cm2/V s, current on/off ratios of >107, and external quantum efficiency of 10-2% at 2100 cd/m2. These combined optical and electrical performance exceed those reported to date for HLETs. Furthermore, we provide full analysis of charge injection, charge transport, and recombination mechanism of the HLETs. The high brightness coupled with a high on/off ratio and low-cost solution processing makes this type of hybrid device attractive from a manufacturing perspective.open0

Swapping field-effect transistor characteristics in polymeric diketopyrrolopyrrole semiconductors: Debut of an electron dominant transporting polymer

A fact-finding study on thiophenyl diketopyrrolopyrrole (TDPP)-containing polymers for electronically convertible transport characteristics in organic field effect transistors (OFETs) is presented. In the subject of this consideration, a TDPP-based polymer with bis-benzothiadiazole (BisBT) units that serve as powerful electron-deficient building blocks, namely PDTDPP-BisBT, is prepared in order to achieve an n-channel transistor. The resulting polymer shows n-channel dominant ambipolar OFET characteristics and its electron mobility (1.3 x 10(-3) cm(2) V(-1) s(-1)) is found to be one order of magnitude higher than the hole mobility. Besides, the PDTDPP-BisBT OFET performance is independent of film-deposition conditions due to its completely amorphous microstructure, supported by the atomic force microscopy (AFM) and X-ray diffraction (XRD) analyses. Herein, we report an intriguing discovery in sync with our previous studies that TDPP-based polymers can function as a p-type, n-type, or ambipolar organic semiconductor in accordance with the degree of electron affinity of the comonomers.close211

Observation of ambipolar field-effect behavior in donor-acceptor conjugated copolymers

Although donor (D)-acceptor (A) conjugated copolymers possess an electron deficient unit, most D-A copolymers exhibit only hole transport properties (p-type). While there are some D-A copolymers that show ambipolarity, n-type behaviour is highly dependent on the type of acceptor used. In this work, ambipolar field-effect behaviour was derived from general D-A conjugated copolymers, believed to be a typical p-type material, by introducing a functional passivation layer between gate dielectric and active layers using polypropylene-co-1-butene (PPcB). The PPcB layer effectively covered the hydroxyl groups and induced a reduction in the energetic disorder at the semiconductor-insulator interface. As a result, the FET devices fabricated using D-A conjugated copolymers, such as PCDTBT, PTBT and Si-PCPDTBT, showed clear ambipolar properties.close2

Efficient and Moisture-Stable Inverted Perovskite Solar Cells via n-Type Small-Molecule-Assisted Surface Treatment

Defect states at the surface and grain boundaries of perovskite films have been known to be major determinants impairing the optoelectrical properties of perovskite films and the stability of perovskite solar cells (PeSCs). Herein, an n-type conjugated small-molecule additive based on fused-unit dithienothiophen[3,2-b]-pyrrolobenzothiadiazole-core (JY16) is developed for efficient and stable PeSCs, where JY16 possesses the same backbone as the widely used Y6 but with long-linear n-hexadecyl side chains rather than branched side chains. Upon introducing JY16 into the perovskite films, the electron-donating functional groups of JY16 passivate defect states in perovskite films and increase the grain size of perovskite films through Lewis acid-base interactions. Compared to Y6, JY16 exhibits superior charge mobility owing to its molecular packing ability and prevents decomposition of perovskite films under moisture conditions owing to their hydrophobic characteristics, improving the charge extraction ability and moisture stability of PeSCs. Consequently, the PeSC with JY16 shows a high power conversion efficiency of 21.35%, which is higher than those of the PeSC with Y6 (20.12%) and without any additive (18.12%), and outstanding moisture stability under 25% relative humidity, without encapsulation. The proposed organic semiconducting additive will prove to be crucial for achieving highly efficient and moisture stable PeSCs

Insulin Resistance and Its Association with Metabolic Syndrome in Korean Children

Background. This study investigated the association between insulin resistance (IR) and metabolic syndrome (MetS) in children. Methods. A cross-sectional study involving 1036 healthy children aged between 7 and 13 years was conducted. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated as an index of IR. Participants were classified according to the HOMA-IR quartiles. Results. Incremental, linear trends were found in age (p<0.001), body mass index (BMI) (p<0.001), body fat (p<0.001), waist circumference (p<0.001), resting blood pressures (BP) (p<0.001), triglycerides (TG) (p<0.001), total cholesterol (TC) (p<0.001), high density lipoprotein-cholesterol (HDL-C) (p<0.001), FBG (p<0.001), and insulin (<0.001) according to incremental HOMA-IR categories (from the 1st to 4th quartile). Compared with children in the 1st HOMA-IR quartile, children in the 4th HOMA-IR quartile had significantly higher odd ratios (ORs) of abnormalities in systolic (p=0.051) and diastolic BP (p=0.005), FBG (p<0.001), TG (p<0.001), TC (p=0.016), and HDL-C (p=0.006) even after adjustments for age, gender, BMI, and body fat percentage. Children in the 3rd HOMA-IR quartile had significant abnormalities in FBG (p<0.001), TG (p=0.001), and HDL-C (p=0.010) even after adjustments for the covariates. Conclusion. The current findings suggest that IR is significantly associated with the clustering of MetS risk factors in children in Korea