Yitong Guo

Molecular engineering tuning optoelectronic properties of thieno[3,2-b]thiophenes-based electrochromic polymers

Thieno[3,2-b]thiophene (TT) monomers end-capped with 3,4-ethylenedioxythiophene (EDOT) moieties are electropolymerized to form π-conjugated polymers with distinct electrochromic (EC) properties. Steric and electronic factors (electron donor and acceptor substituents) in the side groups of the TT core, as well as the structure of the polymer backbone strongly affect the electrochemical and optical properties of the polymers and their electrochromic characteristics. The studied polymers show low oxidation potentials, tunable from–0.78 to +0.30 V (vs. Fc/Fc+) and the band gaps from 1.46 to 1.92 eV and demonstrate wide variety of color palettes in polymer films in different states, finely tunable by structural variations in the polymer backbone and the side chains. EC materials of different colors in their doped/dedoped states have been developed (violet, deep blue, light blue, green, brown, purple-red, pinkish-red, orange-red, light gray, cyan and colorless transparent). High optical contrast (up to 79%), short response time (0.57–0.80 s), good cycling stability (up to 91% at 2000 cycles) and high coloration efficiency (up to 234.6 cm2 C–1) have been demonstrated and the influence of different factors on the above parameters of EC polymers have been discussed.

Design and characterization of methoxy modified organic semiconductors based on phenyl[1]benzothieno[3,2-b][1]benzothiophene

Two environmentally and thermally stable [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivatives, BOP-BTBT and DBOP-BTBT are successfully synthesized and analyzed as active layers in organic thin film transistors. The effects of methoxy on BTBT based OTFT materials are reported for the first time. The experimental results show an excellent optimization influence of methoxy group on the OTFT performance with an improved hole transport mobility up to 0.63 cm2 V−1 s−1 (BOP-BTBT) and 3.57 cm2 V−1 s−1 (DBOP-BTBT). Meantime the mono- and bis-substituted derivatives are compared in terms of their physical properties and device performance. We find that the threshold voltage decreases when more methoxy groups are introduced.

Phenyl substitution in tetracene: a promising strategy to boost charge mobility in thin film transistors

Tetracene, one of the polyacene derivatives, shows eminent optical and electronic properties with relatively high stability. To take advantage of the intrinsic properties of the tetracene molecule and explore new semiconductors, herein, we report the design and synthesis of two novel p-channel tetracene derivatives, 2-(4-dodecyl-phenyl)-tetracene (C12-Ph-TET) and 2-phenyl-tetracene (Ph-TET). Top contact OTFTs were fabricated using these two materials as semiconductor layers, with charge mobilities up to 1.80 cm2 V−1 s−1 and 1.08 cm2 V−1 s−1, respectively. Our molecular modeling results indicate that the introduction of phenyl into tetracene can improve the efficient charge transport in electronic devices as a result of the increased electronic coupling between the two neighboring planes of the molecules. AFM images of the thermally evaporated thin films of these two materials show large grains, which correspond to the high mobilities of these devices. Consequently, the mobility of our OTFTs based on C12-Ph-TET is the highest for OTFTs based on tetracene derivatives reported to date. The single crystal analyses show the existence of π–π stacking interactions within the molecules with the introduction of mono-phenyl substituents, which is the main cause of the increased mobility. The impressive properties of these two materials indicate that the introduction of alkyl-phenyl and phenyl group could be an excellent method to improve the properties of the organic semiconductor materials.

A smart polymer with a high sensitivity to temperature and humidity based on polyacrylamide hydrogel doped with polyiodide

A smart polymer is developed by in situ fabrication of polyacrylamide hydrogel with polyiodide. The resulting PAM hydrogel doped with polyiodide showed a high sensitivity to temperature and humidity. Its special humidity-response behavior with high responsivity makes the described hydrogel a highly promising material for building temperature- and humidity-control switches.