Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.

Flexible, thin-film electronic and optoelectronic devices typically involve a trade-off between performance and fabrication cost. For example, solution-based deposition allows semiconductors to be patterned onto large-area substrates to make solar cells and displays, but the electron mobility in solution-deposited semiconductor layers is much lower than in semiconductors grown at high temperatures from the gas phase. Here, we report band-like electron transport in arrays of colloidal cadmium selenide nanocrystals capped with the molecular metal chalcogenide complex In(2)Se(4)(2-), and measure electron mobilities as high as 16 cm(2) V(-1) s(-1), which is about an order of magnitude higher than in the best solution-processed organic and nanocrystal devices so far. We also use CdSe/CdS core-shell nanoparticles with In(2)Se(4)(2-) ligands to build photodetectors with normalized detectivity D* > 1 × 10(13) Jones (I Jones = 1 cm Hz(1/2) W(-1)), which is a record for II-VI nanocrystals. Our approach does not require high processing temperatures, and can be extended to different nanocrystals and inorganic surface ligands.

Colloidal semiconductor nanocrystals (NCs) provide convenient "building blocks" for solution-processed solar cells, light-emitting devices, photocatalytic systems, etc. The use of inorganic ligands for colloidal NCs dramatically improved inter-NC charge transport, enabling fast progress in NC-based devices. Typical inorganic ligands (e.g., Sn(2)S(6)(4-), S(2-)) are represented by negatively charged ions that bind covalently to electrophilic metal surface sites. The binding of inorganic charged species to the NC surface provides electrostatic stabilization of NC colloids in polar solvents without introducing insulating barriers between NCs. In this work we show that cationic species needed for electrostatic balance of NC surface charges can also be employed for engineering almost every property of all-inorganic NCs and NC solids, including photoluminescence efficiency, electron mobility, doping, magnetic susceptibility, and electrocatalytic performance. We used a suite of experimental techniques to elucidate the impact of various metal ions on the characteristics of all-inorganic NCs and developed strategies for engineering and optimizing NC-based materials.

High-mobility solution-processed all-inorganic solid state nanocrystal (NC) transistors with low operation voltage and near-zero hysteresis are demonstrated using high-capacitance ZrO(x) and hydroxyl-free Cytop gate dielectric materials. The use of inorganic capping ligands (In(2)Se(4)(2-) and S(2-)) allowed us to achieve high electron mobility in the arrays of solution-processed CdSe nanocrystals. We also studied the hysteresis behavior and switching speed of NC-based field effect devices. Collectively, these analyses helped to understand the charge transport and trapping mechanisms in all-inorganic NCs arrays. Finally, we have examined the rapid thermal annealing as an approach toward high-performance solution-processed NCs-based devices and demonstrated transistor operation with mobility above 30 cm(2)/(V s) without compromising low operation voltage and hysteresis.

Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al2O3 films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al2O3 films are significantly corroded by water. In this study, we examined the deformation of PEALD Al2O3 films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al2O3/TiO2 nanolamination (NL) technique. Our Al2O3/TiO2 NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated.

No abstract

A new polymeric semiconductor, PDPPDTSE, is reported which is composed of a diketopyrrolopyrrole moiety and selenophenylene vinylene selenophene, with a high field-effect mobility achieved through intermolecular donor-acceptor interactions. The field-effect mobility of OFET devices based on PDPPDTSE by spin-casting is 4.97 cm(2) V(-1) s(-1) , which is higher than predecessor polymeric semiconductors.

IntroductionOver the past decade, several conjugated organic oligomers and polymers have been developed for potential use in low-cost semiconductor applications to replace their higher-cost inorganic counterparts. The most attractive aspect of these organic materials is that their structures can be diversifi ed and their physical or chemical properties tuned through strategic molecular design. [1][2][3][4][5][6][7][8][9] Among the variety of organic semiconductors developed, thiophene-based materials have emerged as an important class because of their high chemical and electrochemical stability, the accessibility of their preparation for thiophene synthesis, and the availability of welldeveloped/regioselective ring-ring coupling methodologies. [ 10 , 11 ] Furthermore, the properties of oligo/polythiophene cores can be effi ciently tuned by introducing appropriate substitutions. To date, the fi eld-effect transistor (FET) mobilities in devices composed of oligomeric thiophene semiconductors are generally higher than those obtained from conjugated polymers. Oligomeric thiophene semiconductor polymers engage in longrange packing, and effi cient charge transport is directly related to the long-range packing of molecules in semiconductor fi lms. Many synthetic methods have been developed to functionalize the α -and ω -ends of conjugated thiophene ring systems to increase the solubility and stability toward oxidation or to infl uence the solid-state ordering of oligothiophenes without affecting the planarity of the conjugated backbone. [ 12 , 13 ] The present study was devised based on the following three considerations: i) previously reported organic semiconductors have generally shown J-aggregation [ 14 ] with head-to-tail molecular stacking; [ 15 ] ii) large area π -stacking between adjacent molecules can be realized by H-aggregation, which occurs when molecules stack side by side; [ 16 ] and iii) H-aggregation induces stable morphologies in thin fi lms and reproducible transistor performances. We describe a novel synthetic strategy to induce H-aggregation between adjacent molecules in the thin fi lm state. We designed four types of quaterthiophene derivative with end-groups composed of cyclohexyl ethyl (CE4T), cyclohexyl butyl (CB4T), dicyclohexyl ethyl (DCE4T), and dicyclohexyl butyl (DCB4T). UV-vis absorption and grazing-incidence wideangle X-ray scattering (GIWAXS) analyses indicated that the asymmetric derivatives, CE4T and CB4T, tended to undergo H-Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film TransistorsFour new quaterthiophene derivatives with end-groups composed of dicyclohexyl ethyl (DCE4T), dicyclohexyl butyl (DCB4T), cyclohexyl ethyl (CE4T), and cyclohexyl butyl (CB4T) were designed. All materials showed high solubility in common organic solvents. UV-vis absorption measurements showed that the quaterthiophene derivatives with asymmetrically substituted cyclohexyl end-groups (CE4T and CB4T) preferred H-type aggregation whereas those with symmetrica...