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.

With the emergence of wearable human interface technologies, new applications based on stretchable electronics, such as skin-attached sensors or wearable displays, must be developed. Difficulties associated with developing electronic components with the high stretchabilities required for such applications have restricted the range of appearance and utilization of cost- or process-efficient stretchable electronics. Herein, we present omnidirectionally stretchable wrinkled transistors having a shape that replicates human skin, which operates stably on deformable objects or complex surfaces. Our device offers excellent mechanical and electrical stabilities for preserving relative field-effect mobilities within a standard deviation of nearly 5.6%, under a strain level of up to 62%. Even after 10 000 cycles of stretching to 60% strain, the devices exhibited stable operation with little performance changes. These results indicate that the devices display stretchability properties superior to those of organic transistor arrays by utilizing existing nonstretchable device components.

Asterisk-shaped strain sensors have the recognizabilities of stress degree and direction to overcome the shortcomings of existing strain sensors.

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