Dual nanostructures in poly (3-hexylthiophene) based organic photovoltaics under alternative current electric field

Two-dimensional X-ray diffraction was employed, to provide a complete understanding of the energy efficiency improvement of organic photovoltaics by AC electric field alignment. Two distinguishable poly (3-hexylthiophene) (P3HT) nanostructures were found in the form of two separated layers, one of which is highly oriented and the other randomly distributed. The finding helps to analyze the crystallite arrangements not only in the interface in the bulk heterojunction, but also those closer to the substrate. The highly oriented P3HT layer, although located near the substrate, was found to enhance the device efficiency, by increasing the short circuit current and decreasing the series resistance.     

Poly(3-hexylthiophene) based field-effect transistors with gate SiO2 dielectric modified by multi-layers of 3-aminopropyltrimethoxysilane

Top-contact organic field-effect transistors based on poly(3-hexylthiophene) (P3HT) active layer were fabricated using gate dielectric (SiO₂) modified with 3-aminopropyltrimethoxysilane (APTMS) multilayers. It has been demonstrated that the treatment of dielectric with APTMS enhances the field-effect mobility as well as the on/off ratio of the devices by nearly two orders of magnitude. This is attributed to conformational changes as well as to an improved uniformity of the spin coat P3HT films on the APTMS-modified substrate as revealed by atomic force microscopy, Fourier transform infrared spectroscopy and UV-Vis measurements.     

Electrical contact properties between the accumulation layer and metal electrodes in ultrathin poly(3-hexylthiophene)(P3HT) field effect transistors

Probing contact properties between an ultrathin conjugated polymer film and metal electrodes in field effect transistors (FETs) is crucial not only to understanding charge transport properties in the accumulation layer but also in building organic sensors with high sensitivity. We investigated the contact properties between gold electrodes and poly(3-hexylthiophene) (P3HT) as a function of film thickness using gated four-point sheet resistance measurements. In an FET with a 2 nm thick P3HT film, a large voltage drop of 1.9 V (V(D) = -3 V) corresponding to a contact resistance of 2.3 × 10(8) Ω was observed. An effective FET mobility of 1.4 × 10(-3) cm(2)/(V s) was calculated when the voltage drop at the contacts was factored out, which is approximately a factor of 3 greater than the two-contact FET mobility of 5.5 × 10(-4) cm(2)/(V s). A sharp decrease in the ratio of the contact resistance to the channel resistance was observed with increasing film thickness up to a thickness of approximately 6 nm, separating a contact limited regime from a charge transport limited regime. The origin of the large contact resistance observed in the device prepared with an ultrathin P3HT film is discussed in light of results from X-ray diffraction (XRD) and atomic force microscopy (AFM) studies.     

Hole transport in organic field-effect transistors with active poly(3-hexylthiophene) layer containing CdSe quantum dots

Hybrid field-effect transistors (FETs) based on poly(3-hexylthiophene) (P3HT) containing CdSe quantum dots (QDs) were fabricated. The effect of the concentration of QDs on charge transport in the hybrid material was studied. The influence of the QDs capping ligand on charge transport parameters was investigated by replacing the conventional trioctylphosphine oxide (TOPO) surfactant with pyridine to provide closer contact between the organic and inorganic components. Electrical parameters of FETs with an active layer made of P3HT:CdSe QDs blend were determined, showing field-effect hole mobilities up to 1.1×10^?4 cm²/Vs. Incorporation of TOPO covered CdSe QDs decreased the charge carrier mobility while the pyridine covered CdSe QDs did not alter this transport parameter significantly.     

Thermophysical properties of free-standing micrometer-thick Poly(3-hexylthiophene) films

The solution of Poly(3-hexylthiophene) (P3HT) in chloroform is generally adopted for fabricating P3HT thin films or nanofibers. In this work, 4 regular P3HT solution weight percentages, 2, 3, 5 and 7 wt.%, are compounded to fabricate P3HT thin films by using spin-coating technique. Raman spectrum study suggests that the density of the P3HT thin films varies with different P3HT solution weight percentages while X-ray diffraction analysis reveals that the crystal structures are identical for all P3HT thin films. The transient electrothermal technique is employed to measure the thermal diffusivity of the P3HT thin films and an efficient temperature-resistance calibration is performed to cooperatively study the thermal conductivity. When the P3HT weight percentage changes from 2% to 7%, the thermal conductivity varies from 1.29 W/m·K to 1.67 W/m·K and the thermal diffusivity goes down from around 10^− 6 m²/s to 5 × 10^− 7 m²/s. The density of P3HT thin films is also determined from the experimental data. The relationship between the density and thermophysical properties clearly demonstrates that the thermal conductivity increases with density while the thermal diffusivity decreases.     

Enhancement of carrier mobility in all-inkjet-printed organic thin-film transistors using a blend of poly(3-hexylthiophene) and carbon nanoparticles

To enhance the carrier mobility of all-inkjet-printed organic thin film transistors, we fabricated devices that incorporated poly(3-hexylthiophene) (P3HT) and carbon nanoparticles (CNPs). The fabricated devices had an on/off ratio of 10⁴, which is one order less than that of pristine organic thin-film transistors (OTFTs). The maximum carrier mobility as high as 0.053 cm²/V-s was achieved for a CNP/P3HT weight-weight ratio of 7/100. This degree of mobility is 10 times greater than average mobility of pristine P3HT-OTFTs. X-ray diffraction and scanning electron microscopy images reveal that the carrier mobility was enhanced by reducing the injection barrier and enhancing the carrier injection. This work demonstrates the feasibility of all-inkjet-printed OTFT technology.     

Thermal annealing time effect on the performance of ambipolar organic light-emitting transistors based on conjugated polymer blends

Here we report the effect of thermal annealing time on the performance of ambipolar organic light-emitting transistors (OLETs) made using conjugated polymer blends. Regioregular poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorenyl-2,3-diyl-co-1,4-benzo-2,1',3-thiadiazole) (F8BT) were chosen as a p-type and a n-type component, respectively. As a gate insulator, poly(4,4'-oxydiphenylene-pyromellitimide) (PMDA-ODA PI) was employed due to its high solvent resistance and thermal stability. Results showed that the present OLETs exhibited ambipolar characteristics even after thermal annealing. All devices showed almost identical field-effect mobility for both holes and electrons. The highest field-effect mobility was achieved for the OLET annealed at 130 degrees C for 60 min, which was assigned to the improved polymer-metal contact by thermal annealing leading to better charge injection.     

Comparative behavior of CdS and CdSe quantum dots in poly(3-hexylthiophene) based nanocomposites

CdS and CdSe nanoparticles have been prepared using conducting poly(3-hexylthiophene) (P3HT) matrix with an objective to understand the effect of nanoparticles on the polymer matrix using electrochemical and spectroscopic techniques. The spectroscopic results reveal that the electronic structure of polymer is strongly influenced by the characteristics of embedded semiconducting nanoparticles. SEM and TEM images show the ordered morphology of the CdS and CdSe nanoparticles in presence of the polymer matrix. Cyclic voltammetry performed both in the presence and absence of light enables us to understand the redox changes in P3HT due to CdS and CdSe quantum dots such as the generation of free radical in the excited state and their electrochemical band gaps.     

The role of solvent and morphology on miscibility of methanofullerene and poly(3-hexylthiophene)

A bicontinuous, percolating bulk heterojunction morphology is integral to organic polymer solar cells. Understanding the factors affecting the miscibility of photovoltaic polymers with a fullerene electron acceptor molecule is a key to controlling the morphology. Starting from discreet pure phases - a poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) bilayer film - the evolution of the P3HT-PCBM interface was studied with particular attention to the role of residual solvent in P3HT on PCBM interdiffusion. This investigation shows that in the bilayer geometry PCBM can rapidly diffuse into amorphous P3HT, but phase separation is maintained if the P3HT layer is cast from a very volatile solvent or if it is annealed prior to casting the PCBM overlayer to complete the bilayer geometry.     

Effect of self-assembled monolayers on charge injection and transport in poly(3-hexylthiophene)-based field-effect transistors at different channel length scales

Charge injection and transport in bottom-contact regioregular-poly(3-hexylthiophene) (rr-P3HT) based field-effect transistors (FETs), wherein the Au source and drain contacts are modified by self-assembled monolayers (SAMs), is reported at different channel length scales. Ultraviolet photoelectron spectroscopy is used to measure the change in metal work function upon treatment with four SAMs consisting of thiol-adsorbates of different chemical composition. Treatment of FETs with electron-poor (electron-rich) SAMs resulted in an increase (decrease) in contact metal work function because of the electron-withdrawing (-donating) tendency of the polar molecules. The change in metal work function affects charge injection and is reflected in the form of the modulation of the contact resistance, R(C). For example, R(C) decreased to 0.18 MΩ in the case of the (electron-poor) 3,5-bis-trifluoromethylbenzenethiol treated contacts from the value of 0.61 MΩ measured in the case of clean Au-contacts, whereas it increased to 0.97 MΩ in the case of the (electron-rich) 3-thiomethylthiophene treated contacts. Field-effect mobility values are observed to be affected in short-channel devices (<20 μm) but not in long-channel devices. This channel-length-dependent behavior of mobility is attributed to grain-boundary limited charge transport at longer channel lengths in these devices.     

Stability and 2,4-dinitrotoluene response of organic field effect transistors based on π-conjugated thiophene oligomers

This paper reports on organic field effect transistors (OFETs) based on two π-conjugated oligomers derived from thiophenes and their use as sensors for the detection of 2,4-dinitrotoluene (DNT). The detection mechanism relies on donor-acceptor interactions between the π-conjugated system (donor) and the nitrated molecule (acceptor). An important feature of sensors is the stability under operation, so, a large part of this work will be dealing with the behavior of OFETs under bias stress experiments as well as with the influence of temperature during operation. Most of results reported here are concerning hexyl capped tetra Thienylene–Vinylene (denominated 4-TV). Some preliminary results on the promising hexyl capped quinquethiophene derived from 3,4-ethylenedioxythiophene (denominated TETET) are also reported. Under a DNT contaminated air atmosphere ( 7 ppm), 4-TV based OFETs exhibit an increase of the drain current when DNT is present in the atmosphere as expected.     

The Influence of the Morphology on the Magnetic Properties of Poly(3-hexylthiophene)

The influence of the morphology on the magnetic properties of poly(3-hexylthiophene) has been studied and the results reported. The changes in the saturation magnetization were explained considering the polymer morphology prepared with different amounts of water in the solution during sample synthesis. The results show that the saturation magnetization is maximized for 200 ppm of the water in acetonitrile solution.     

Controllable and reproducible fabrication of high anisotropic organic field effect transistors

Increasing the alignment of thin films, which leads to anisotropy, is an attractive way to improve the performance of organic devices. A highly controllable and reproducible method to fabricate organic field effect transistors with large anisotropic ratios was proposed in this paper. The surface of the dielectric layer was etched to form patterns through conventional semiconductor processing. Transistors having current direction perpendicular to or parallel to the direction of the patterns were fabricated and characterized. The mobilities of these two kinds of transistors are 0.016 and 0.001 cm²/Vs respectively, which means the anisotropic ratio is 16.     

聚3-己基噻吩的光电性能研究

利用光电化学方法研究了聚3-己基噻吩的光电化学性质,其禁带宽度为1.89eV,同时确定了它的价带位置(-3.6eV)、导带位置(-5.4eV).研究发现聚3-己基噻吩属于直接跃迁型半导体,在本文条件下得到的最高IPCE值达5.2%     

Fabrication of calcium ion sensitive diamond field effect transistors (FETs) based on immobilized calmodulin

We have developed calcium (Ca²⁺) ion sensitive solution-gate field effect transistors (SGFETs) on polycrystalline diamond by using partial amination and immobilization of calmodulin (CaM), a specific protein to calcium ions. The CaM is covalently immobilized on functionalized diamond surface, and the functionalized surface was analyzed by X-ray photoelectron spectroscopy, respectively. Also, the high performance of the CaM-immobilized diamond SGFET for detecting Ca²⁺ were studied with respect to high selectivity and sensitivity in various concentrations and pH.     

合成方法对聚(3-己基噻吩)立构规整度的影响

采用化学氧化法、格式反应法、GRIM (Grignard Metathesis Method)法和超声辅助GRIM法、合成了不同立构规整度的聚3-己基噻吩(P3HT).用GPC、紫外-可见光谱、红外光谱(FT-IR)和核磁共振谱(1 H-NMR)对P3HT的分子结构和立构规整度进行了表征.结果表明,GRIM法合成的P3...     

Microdisk laser emission and electrical properties of composite films based on poly(3-hexylthiophene)s with different stereoregularity

The optical and electrical properties of composite thin films of poly(3-hexylthiophene)s (PAT6s), processing different stereo-regularity originating from side-chain regio orders have been studied. The laser emission properties of PAT6 composite thin films in microdisk structure have been observed by pulsed photopumping. From the electrical and optical measurements, the electrical conductivity and the quantum efficiency of the PAT6 composite films were estimated. The emission and conductivity depending on the mixture ratios were discussed by taking the stereo-regularity of the molecular structure into consideration.