Organic semiconductor crystals

Abstract

Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

Organic Single‐Crystalline Semiconductors for Light‐Emitting Applications: Recent Advances and Developments

“…As was mentioned above, all three crystal‐growth methods have the potential for the development of large‐area crystals. However, to date, the research on this field is slow going, and there remain some challenges . In the solution‐processing method, if the material in‐plane intermolecular interactions are much stronger than the out‐of‐plane ones, it is possible to self‐assemble the molecules into large‐area crystals due to the strong dominating intermolecular interactions.…”

“…b) Schematic diagram of the drop‐casting method by pouring a saturated precursor solution on substrates for crystal nuclei formation. a,b) Reproduced with permission . Copyright 2017, The Royal Society of Chemistry.…”

“…Among them, organic single‐crystalline semiconductors (OSCSs) constructed by π‐conjugated molecules in long‐range periodic order have emerged as a unique optoelectrical material . Their defined structures provide an opportunity to investigate the impact of the basic molecular interactions on the structure–property relationships and reveal fundamental physics in organic semiconductors.…”

“…In early research, OSCSs served as a powerful tool for evaluating the intrinsic charge‐transport mechanisms of organic semiconductors. The surface charge transport of these materials was determined based on the technology of field‐effect transistors with recorded mobility reaching up to 43 cm 2 V −1 s −1 . Later, they have emerged as a hotspot in the field of optically pumped lasers, which stemmed from the discovery of amplified spontaneous emission (ASE) phenomena and lasing oscillations .…”

“…This enthusiasm for the study of OSCSs has extended the applications range to various high‐performance and low‐cost optoelectronic devices. A series of broad reviews highlighting the most important progress obtained by OSCSs has finished in different aspects including growth strategies, materials design, and device applications . However, none of the reviews so far has focused on the electrical‐pumping light‐emitting behavior, which is not only scientifically important but also technologically imperative for EL devices.…”