Attaining Melt Processing of Complementary Semiconducting Polymer Blends at 130 °C via Side-Chain Engineering

Complementary semiconducting polymer blends (c-SPBs) have been proposed and tested to achieve melt-processed high-performance organic field-effect transistors (OFETs). Prior to this study, melt processing requires temperatures as high as 180 °C. To implement this technique into low-cost and large-area thin-film manufacturing for flexible organic electronics, semiconducting materials meltable at temperatures tolerable by ubiquitous plastic substrates are still needed. We report here the design and melt processing of a c-SPB consisting of a matrix polymer (DPP-C5) and its fully conjugated analogue. By utilizing a siloxane-terminated alkyl chain and a branched alkyl chain as solubilizing groups, the matrix polymer DPP-C5 presents a melting temperature of 115 °C. The resulting c-SPB containing as low as 5% of the fully conjugated polymer could be melt-processed at 130 °C. The obtained OFET devices exhibit hole mobility approaching 1.0 cm²/(V s), threshold voltages below 5 V, and I_ON/I_OFF around 10⁵. This combination of efficient charge-carrier transport and considerably low processing temperatures bode well for melt processing of semiconducting polymer-based organic electronics.

Organic Field-Effect Transistors with Macroporous Semiconductor Films as High-Performance Humidity Sensors

In this study, we designed and fabricated a high-performance humidity sensor based on a donor-acceptor polymer transistor. To improve its sensing performance, a polymeric semiconductor film with macroporous structure was prepared using a facilitated phase-separation method. The relationship between the sensing performance and the pore size was systematically investigated by testing the humidity-sensing performance. The results suggested that the sensitivity of the sensor was improved with increasing pore size within a certain range. The sensor based on the macroporous film with an average pore size of 154 nm exhibited a sensitivity of 415 and a response time of 0.68 s, as the low relative humidity (RH) changed from 32% RH (9146 ppm) to 69% RH (20 036 ppm). These sensitivity values are better than those obtained by other reported humidity sensors based on organic field-effect transistors.

Melt-Processing of Complementary Semiconducting Polymer Blends for High Performance Organic Transistors

Melt-processing of complementary semiconducting polymer blends provides an average charge carrier mobility of 0.4 cm² V^-1 s^-1 and current on/off ratios higher than 10⁵ , a record performance for melt-processed organic field-effect transistors.

Microstructural control over soluble pentacene deposited by capillary pen printing for organic electronics

Research into printing techniques has received special attention for the commercialization of cost-efficient organic electronics. Here, we have developed a capillary pen printing technique to realize a large-area pattern array of organic transistors and systematically investigated self-organization behavior of printed soluble organic semiconductor ink. The capillary pen-printed deposits of organic semiconductor, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS_PEN), was well-optimized in terms of morphological and microstructural properties by using ink with mixed solvents of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB). Especially, a 1:1 solvent ratio results in the best transistor performances. This result is attributed to the unique evaporation characteristics of the TIPS_PEN deposits where fast evaporation of CB induces a morphological evolution at the initial printed position, and the remaining DCB with slow evaporation rate offers a favorable crystal evolution at the pinned position. Finally, a large-area transistor array was facilely fabricated by drawing organic electrodes and active layers with a versatile capillary pen. Our approach provides an efficient printing technique for fabricating large-area arrays of organic electronics and further suggests a methodology to enhance their performances by microstructural control of the printed organic semiconducting deposits.