An eco-friendly biodegradable starch paper is introduced for use in nextgeneration disposable organic electronics without the need for a planarizing layer. The starch papers are formed by starch gelatinization using a very small amount of 0.5 wt% polyvinyl alcohol (PVA), a polymer that bound to the starch, and 5 wt% of a crosslinker that bound to the PVA to improve mechanical properties. This process minimizes the additions of synthetic materials. The resultant starch paper provides a remarkable mechanical strength and stability under repeated movements. Robustness tests using various chemical solvents are conducted by immersing the starch paper for 6 h. Excellent nonpolar solvent stabilities are observed. They are important for the manufacture of organic electronics that use nonpolar solution processes. The applicability of the starch paper as a flexible substrate is tested by fabricating flexible organic transistors using pentacene, dinaphtho[2,3-b:2′,3′-f ]thieno[3,2-b]thiophene, and poly(dimethyltriarylamine) using both vacuum and solution processes. Electrically well-behaved device performances are identified. Finally, the eco-friendly biodegradability is verified by subjecting the starch paper to complete degradation by fungi in fishbowl water over 24 d. These developments illuminate new research areas in the field of biodegradable green electronics, enabling the development of extremely low-cost electronics.

Wrinkled elastomeric templates prepared by stretching and releasing are utilized for demonstrating highly sensitive, simple, and low-cost piezocapacitive pressure sensors over large area.

Printing technologies are instrumental to the fabrication of low‐cost lightweight flexible electronic devices and circuits, which are necessary to produce wearable electronic applications. However, attaining fully printed devices on flexible films over large areas has typically been a challenge. Here, the fabrication of fully drawn all‐organic field‐effect transistor (FET) arrays on mechanically flexible substrates using a capillary‐pen printing method is demonstrated. A highly crystalline organic semiconductor (active layer), a smooth insulating polymer (dielectric layer), and a conducting polymer (source, drain, and gate electrodes) are deposited from solution sequentially. The bottom‐gate bottom‐contact FETs drawn onto flexible substrates exhibit superior field‐effect mobilities of up to 0.54 cm2 V−1 s−1, good reproducibility, operational stability, and mechanical bendability. Furthermore, to emphasize the methodological advantages of the capillary‐pen printing, an organic FET (OFET) array on a curvilinear substrate of a plastic straw and the repairing concept for a broken electrical circuit are demonstrated. These results indicate that capillary pen printing shows promise as a manufacturing technique for a wide range of large‐area electronic applications.

The introduction of an appropriate functionality on the electrode/active layer interface has been found to be an efficient methodology to enhance the electrical performances of organic field-effect transistors (OFETs). Herein, we efficiently optimized the charge injection/extraction characteristics of source/drain (S/D) electrodes by applying an asymmetric functionalization at each individual electrode/organic semiconductor (OSC) interface. To further clarify the functionalizing effects of the electrode/OSC interface, we systematically designed five different OFETs: one with pristine S/ D electrodes (denoted as pristine S/D) and the remaining ones made by symmetrically or asymmetrically functionalizing the S/D electrodes with up to two different self-assembled monolayers (SAMs) based on thiolated molecules, the strongly electron-donating thiophenol (TP) and electron-withdrawing 2,3,4,5-pentafluorobenzenethiol (PFBT). Both the S and D electrodes were functionalized with TP (denoted as TP-S/D) in one of the two symmetric cases and with PFBT in the other (PFBT-S/D). In each of the two asymmetric cases, one of the S/D electrodes was functionalized with TP and the other with PFBT (to produce PFBT-S/TP-D and TP-S/PFBT-D OFETs). The vapor-deposited p-type dinaphtho[2,3-b:2′,3′f ]thieno[3,2-b]thiophene was used as the OSC active layer. The PFBT-S/TP-D case exhibited a field-effect mobility (μ FET ) of 0.86 ± 0.23 cm 2 V −1 s −1 , about three times better than that of the pristine S/D case (0.31 ± 0.12 cm 2 V −1 s −1 ). On the other hand, the μ FET of the TP-S/PFBT-D case (0.18 ± 0.10 cm 2 V −1 s −1 ) was significantly lower than that of the pristine case and even lower than those of the TP-S/D (0.23 ± 0.07 cm 2 V −1 s −1 ) and PFBT-S/D (0.58 ± 0.19 cm 2 V −1 s −1 ) cases. These results were clearly correlated with the additional hole density, surface potential, and effective work function. In addition, the contact resistance (R C ) for the asymmetric PFBT-S/TP-D case was 10-fold less than that for the TP-S/PFBT-D case and more than five times lower than that for the pristine case. The results contribute a meaningful step forward in improving the electrical performances of various organic electronics such as OFETs, inverters, solar cells, and sensors.

Here, a stretchable organic field‐effect transistor (OFET) that exhibits constant electrical performance irrespective of the strain direction is demonstrated. The device is integrated onto an elastomer template with randomly oriented wrinkles on its surface; these wrinkles are spontaneously formed because of the differences in the thermal–mechanical properties of the plastic layer and the underlying elastomer. To achieve this microtopography, a relatively hard polymer, Parylene C, is ad‐deposited onto an elastomer blended with polydimethylsiloxane and Ecoflex, resulting in PD‐flex. Consequently, this microtopography offers stable device operations of a dinaphtho[2,3‐b:2′,3′‐f  ]thieno[3,2‐b]thiophene OFET array under 5% elongation irrespective of strain direction. Furthermore, the electrical performance is highly stable during 10 000 cycles of uniaxial strain, as verified by negligible modulation of the device's field‐effect mobility, threshold voltage, and drain‐current maximum. This approach allows nonstretchable device components to be relevant to stretchable electronics. More importantly, it is highly compatible to device alignment and provides stability under various kinds of mechanical deformations.