Organic light-emitting diodes (OLEDs), as the basic unit of flexible display technology, have shown tremendous applications in cell phone display, folding, and wearable display applications, and have formed a trillion-dollar electronics industry. Polymer Light Emitting Diode (PLED) based intrinsically flexible displays, as an important future development direction for the flexible electronics industry, show important application potential in more comfortable biomedical, wearable and smart conformal displays. Display devices made of stretchable materials can be expected to have greater free volume in foldable, stretchable and seamless docking, allowing direct visual interaction and three-dimensional views. The use of stretchable technology to fabricate stretchable transistor active matrices will facilitate the rapid development of intrinsically stretchable displays. However, the development of intrinsically flexible active matrix PLEDs faces great challenges due to the limited scalability of PLEDs and the difficulty of obtaining intrinsically flexible light-emitting semiconductors.

With the support of the National Natural Science Foundation of China, the Ministry of Science and Technology, and the Chinese Academy of Sciences, the team of researcher Yunlong Guo and academician Yunqi Liu at the Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, based on the previous work on tuning the condensed structure of polymer semiconductors to enhance homogeneity (Adv. Electron. Mater. 2022, 8, 2100881.), developed a high molecular weight phenylene braced ethylene (L-SY) based molecular weight phenylene braced vinyl (L-SY-PPV) and polyacrylonitrile (PAN) polymers in a self-assembled three-dimensional penetrating nanonetwork to simultaneously enhance stretchability and carrier mobility (Figure 1). Typically, the improved stretchability of conventional light-emitting polymers is accompanied by a reduction in charge transport capability, which leads to a significant reduction in device efficiency. In this study, the three-dimensional penetrating nanonetworks formed by PAN resulted in a 5-6 fold increase in carrier mobility and stretchability from 20% (pristine L-SY-PPV film) to 100% for L-SY-PPV/PAN. Further incorporation of polyethyleneimine ethoxylated Zn-PEIE-pBphen-TR as an intrinsically stretched electron injection layer successfully constructed intrinsically stretched PLEDs with high current efficiency.These results demonstrate the effectiveness of using self-assembled 3D penetrating nanonetworks to fabricate intrinsically flexible PLEDs. The related research results were published in the recent Adv. Mater. (2022, DOI: 10.1002/adma.202201844), which was first authored by Yanwei Liu, a PhD student, and correspondingly by Yunlong Guo, a researcher, and Yunqi Liu, an academician. 

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