A new method for synthesis of perylene-3,4-dicarboximides (PDCIs) is reported. Modified from a literature reported synthetic method, microwave assisted heating was used to perform the reaction, which not only shortened the original reaction time, from 18 hours to 30 min, but also increased the corresponding reaction yield. A variety of PDCI derivatives were synthesized in order to correlate the influence of substituents on the reaction outcome. Moreover, the photophysical and electrochemical properties of PDCIs are characterized and reported.

Gating organic transistors with electric double layers (EDL) of electrolytes is advantageous in injecting high-density carriers with the application of minimum gate voltage. The drawback of such devices, however, has been that commonly used polymer electrolytes suffer relatively slow ionic diffusion before forming the EDLs. In this report, we disclose a new class of EDL devices incorporating low-viscosity room temperature ionic liquid as the electrolyte layer, so that the rapid ionic diffusion allows MHz operation for the transistor performance. We fabricate a well structure using an elastomeric rubber stamp of poly-dimethylsiloxane to hold the ionic liquid 1-ethyl 3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide, known for high ionic conductivity. The transistor performs without hysteresis with the carrier mobility of 5 cm2V−1s−1, realizing the highest sheet transconductance ever achieved.

Polysilanes, being ó bonded, are promising materials for emission in ultraviolet/near ultraviolet (UV/NUV) region and exhibit adequate charge mobility for fabricating practical devices. This study contributes to the understanding of the effects of thermal annealing on the performance of organic light-emitting diodes (OLEDs) made of poly (n-butylphenyl-silane) (PS-4). OLEDs having indium tin oxide (ITO)/poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate) PEDOT: PSS/poly (n-butylphenylsilane) (PS-4)/lithium fluoride (LiF)/Al device structure were fabricated. PS-4 is spin coated and annealed for one hour at different temperatures (90-120°C). EL Spectra from these devices consists of white emission along with the UV peak. Current density-voltage (J-V), photoluminescence (PL) and electroluminescence (EL) spectra are also measured. White emission is significantly suppressed when PS-4 is annealed at higher temperature and threshold voltage is lowest at 110°C annealing temperature. This is correlated with PL emission and structural properties of PS-4 films. Surface morphology of PS-4 was measured using atomic force microscopy (AFM). The results are explained in terms of effect of annealing of polymer films on interchain interactions.

This work studied systemically the device characteristics when the OFETs' channels turn into hundreds of nm. Standard planar OFETs have been fabricated using electronic beam lithography. Copper phthalocyanine is used as the semiconductor materials. When reduce the L to about 300 nm will lead an abrupt degradation of device performance. The ratio of Ion/Ioff turns from several hundreds into couple of tens. And when change the L to about 100 nm, the mobility turns from 10−2 cm2/Vs into 10m5 cm2/Vs, and the threshold voltage turns from about 12 V into 36 V. These abrupt changes are due to the changes of interface between active layer and insulator layer caused by the reducing the L to close to the grain size.

We report herein the results of density functional theory calculations of the geometric and electronic structure for a series of fused heterocyclic compounds. These molecules were compared with the corresponding carbocyclic oligoacenes, which are currently being experimentally investigated for use as organic semiconductors. The impact of various structural modifications on this class of compounds on the calculated structures is examined. The results of our calculations reveal that such materials hold exceptional promise as organic semiconductors.

Poly(vinyl alcohol) (PVA) is a water based dielectric often used as a coating layer in paper industry. Due to its water solubility PVA is also interesting as gate insulator in organic field effect transistors. Depending on the preparation of the PVA gate, transistors with and without hysteresis can be produced, with applications in organic electronic circuits or memory elements. In the production of PVA, a major side product is sodium acetate, an ionic salt not completely removed during industrial purification. Such ionic impurities likely influence the hysteresis in PVA based organic field effect transistors. While a hysteresis is desirable in memory elements it is unwanted in transistors for electronic circuits. Ways to prepare transistors with a desired transfer characteristic are described, for example by using electronic grade products directly from the purchaser of PVA, or by employing PVA purified by means of dialysis. Measurements are performed with metal-insulator-metal (MIM) structures and organic field effect transistors (OFETs), where Buckminsterfullerene C60 is employed as organic semiconductor.

Pentacene is one of the most studied semiconductor for organic thin-film transistors (OTFTs), and enhanced understanding of pentacene-based TFTs has significantly advanced the organic electronics. We report here the crucial effect of the polymer gate dielectric glass transition temperature (Tg) on pentacene film growth mode, microstructure, and the resulting TFT performance. Nanoscopically-confined thin polymer films are known to exhibit reduced glass-transition temperatures versus the corresponding bulk values, and we demonstrate here that pentacene films grown on polymer gate dielectrics at temperatures well below their bulk Tg exhibit morphological/microstructural transitions and OTFT performance discontinuities at well-defined growth temperatures [defined as the surface Tg, or Tg(s)] characteristic of the underlying polymer structure and independent of the film thickness. The results argue that realistic OTFT response must take into account this fundamental polymer property, and that TFT measurements represent a new probe of polymer surface thermal properties.

Using the time-averaged dielectrophoretic force from an applied electric field, we have observed the assembly of a chemically adsorbed monomolecularlayer (CAM) into microwires, connections, and an electric path according to the location within field regions of a lithographically patterned array of two platinum (Pt) electrodes. A Pt electrode/monolayer/Pt electrode junction was fabricated by the self-assembly of a rigid monomolecular, namely 3-{6-{11-(Trichlorosilyl) undecanoyl} hexyl} thiophene (TEN) with thiophen groups, in the lateral direction between the Pt gap electrodes. The technique of a conductive probe AFM (CP-AFM) has been used to investigate the forward bias conduction properties of a TEN film grown by a wet process deposition on a glass substrate. The self-assembly depends on: (1) the ideal rigidity of the chemically adsorptive monomolecular layer (CAM) and (2) the strong affinity of the thiophen end groups of the CAM for the Pt electrode. The current–voltage (I–V) characteristics of the conjugated thiophen junction exhibited stepwise features at room temperature. The (I–V) characteristics can be explained as an electron transport through the junction. From the results in the atmosphere, the conductivity of a lateral conjugated polythiophen group was calculated to be 5.0×104 S/cm. Understanding and using these effects will allow the controlled fabrication and the positioning of microwires or connections at densities far above what is now achievable.

The performance of the devices of bulk heterojunction polymer-based solar cells were investigated by using poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as light absorption (viz. active) layer, with TiOx as interlayer as follows: ITO/PEDOT:PSS/P3HT-PCBM/TiOx/Al [1] through the treatment of microwave irradiation (single mode of 2.45 GHz, 800 W for 1, 2.5, or 5 min). Such treatments enabled to increase the short-circuit current density Jsc (from 4.53 mA cm−2 to 7.27 mA cm−2) and fill factor FF (from 0.41 to 0.66) of the cell, though the open circuit voltage Voc was decreased (from 0.61 V to 0.57 V) along the irradiation. Absorption spectra of P3HT-PCBM blended film before and after the microwave treatment were observed. Shoulders at 550 nm and 600 nm appeared after the irradiation. This result implies that the microcrystallization of P3HT was slightly promoted through the microwave treatment.

We report a series of our experiments using organic single crystals to reach the maximum performance intrinsic to the materials. A consequence of the experiments is that a prescription for realizing high-mobility devices is to induce carriers in inner crystals to avoid scattering at the surfaces. Intrinsic-semiconductor character of the high-purity organic crystals favors thermal diffusion of the carriers into the crystals in the presence of weak gate-electric fields. Furthermore, it is demonstrated that the high-mobility transport of the in-crystal carriers are highlighted in double-gate single-crystal transistors with the two gate electric field balanced with each other.

Organic field-effect transistors (OFETs) consisted of vacuum-evaporated diethynyl aryl derivatives were prepared and the device characteristics were evaluated. The fabricated OFETs showed typical p-type characteristics for diethynyl naphthalene derivative with two end naphthyl groups. By optimizing the fabrication process, the device exhibited a high field-effect hole mobility up to 0.12 cm2V−1s−1 and a high on/off current ratio of 3.3×105. On the other hand, OFETs showed typical n-type characteristics for diethynyl aryl derivative with two end heptafluoronaphthyl groups. We have observed clear changes from p-channel to n-channel conductions in OFETs by chemically modifying diethynyl aryl derivatives.