Interface stresses are pervasive and critical in conventional optoelectronic devices and generally lead to many failures and reliability problems. However, detection of the interface stress embedded in organic optoelectronic devices is a long-standing problem, which causes the unknown relationship between interface stress and organic device stability (one key and unsettled issue for practical applications). In this study, a kind of previously unknown molecular conformation–induced stress is revealed at the organic embedded interface through sum frequency generation (SFG) spectroscopy technique. This stress can be greater than 10 kcal/mol per nm 2 and is sufficient to induce molecular disorder in the organic semiconductor layer (with energy below 8 kcal/mol per nm 2 ), finally causing instability of the organic transistor. This study not only reveals interface stress in organic devices but also correlates instability of organic devices with the interface stress for the first time, offering an effective solution for improving device stability.
Min Cai,Shuang Nie,Yipu Du,Chengjun Wang,Jizhou Song
Stretchable electronics are of rapidly increasing interest due to their unique ability to function under complex deformations. Strain isolation of stiff functional components from the substrate represents a key challenge in the development of stretchable electronics since their mechanical mismatch may yield undesirable strains to degrade the device performance. The results presented here report an approach to develop a soft strain-isolating polymer substrate with programmable stiffness by spatioselective ultraviolet exposure for stretchable electronics. The approach being compatible with the well-established lithographic process reduces the fabrication complexity significantly and offers a simple yet robust strain-isolation mechanism to ensure the system stretchability of more than 100%. Combined experimental and numerical studies reveal the fundamental aspects of the design, fabrication, and operation of the strain-isolating substrate. Demonstration of this concept in a stretchable inorganic metal-based resistive temperature sensor and a stretchable organic photodiode array with unusually high performance shows the simplicity of the approach and the robustness in strain isolation in both component and device levels. This type of strain-isolation design not only creates promising routes for potential scalable manufacturing of stretchable electronics but also engineering opportunities for stretchable electronics involving the integration of various functional components, which require the quantitative control of the strain levels to achieve optimal performance.
A series of novel discotic liquid-crystalline donor–acceptor dyads (D-A) adjusted by changing the chain length of diester groups on perylene were synthesized based on triphenylene and perylene units which linked by a flexible linkage of 9-nonyloxy-1-amine. The mesomorphism properties and their self-assembly behaviors were studied by differential scanning calorimetry, polarized optical microscopy, one-dimensional wide-angle X-ray diffraction, small angle X-ray scattering and two-dimensional wide-angle X-ray diffraction. Charge carrier mobilities were measured by Time-of-flight device. These discotic liquid crystalline compounds exhibited highly efficient ambipolar charge-transport properties and the charge carrier mobility can reach the order of 10 −4 cm 2 v −1 s −1 by segregated donor–acceptor columns, providing potential utility of the strategy in organic optoelectronic applications.
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