Research progress in intrinsically flexible organic electronic devices

Intrinsically flexible materials are a new generation of functional materials formed by the aggregation of intermolecular or nano elements through weak interactions. Because of their light weight, printability, folding, extensibility, large-area processing, structure function harmony and super flexibility, they are considered to be interdisciplinary science and technology frontier materials. They are widely applied in fields such as information and energy, including flexible displays, healthcare, aerospace, sensing and detection, logical storage, electronic circuits, photovoltaic energy storage, wearable devices, artificial intelligence, and other cutting-edge technology applications, involving interdisciplinary collaborative research in chemistry, physics, materials, biology, semiconductors, microelectronics, and machinery. In recent years, important research achievements in the field of intrinsically flexible organic electronics have been published in high-level domestic and international journals, with research focusing mainly on materials, devices, patterned processes, and circuits. In terms of materials, in order to endow traditional optoelectronic materials with flexibility and stretchability that they do not possess, researchers mainly attempt strategies including molecular design strategies and doping blending strategies. From the perspective of molecular structures, the molecular design strategy optimizes the interaction between molecules by introducing flexible molecular groups to enhance the intrinsic flexibility of materials. In addition, this strategy can also improve the tensile properties of materials by growing originally rigid materials into one-dimensional nanowires or two-dimensional mesh materials. The doping blending strategy mainly studies the interaction between two materials, usually involving the mixing of one material with intrinsic flexibility and another material without intrinsic flexibility. It regulates the phase separation and assembly morphology at the micro scale and improves its tensile properties without sacrificing performance. In terms of devices, there are two widely reported types of intrinsically flexible optoelectronic thin film devices: Transistors and diodes. Intrinsically flexible transistor devices can achieve high-performance optoelectronic detection, low voltage and low power consumption, and synaptic response behavior through optimization of functional and dielectric layers. Intrinsically flexible diode devices can achieve higher luminescence performance and electrochromic function. In terms of patterning processes, patterning processes applied to the preparation of intrinsically flexible materials and devices mainly include lithography, printing, roll to roll, nanoimprinting, oxygen plasma etching, etc. Among them, lithography and printing are the two most widely reported patterning processes and are considered to be effective ways to achieve large-scale integrated applications of intrinsically flexible materials in the future. In terms of circuits, intrinsically flexible circuits are a cutting-edge research field in the discipline, mainly including synaptic neural network circuits, AMOLED driver display circuits, logic gate circuits, etc. Small scale integrated circuits are a key step in the implementation and application of intrinsically flexible optoelectronic materials and organic devices in the future. This review analyzes and discusses the scientific issues and technological bottlenecks in the cutting-edge research field of intrinsically flexible electronic devices, and summarizes and prospects for future application prospects and development trends.