Chiral Conjugated Molecular Assemblies Interact with Substances and Light

Conspectus Chirality has been relevant to numerous core scientific topics over the past century. Recently, the value of chirality in artificial functional materials has been recognized and investigated intensively. Functional materials with chirality demonstrate some characteristic properties lacking in their achiral counterparts. Specifically, in chiral materials, optical rotatory dispersion, circular dichroism (CD), circularly polarized luminescence, nonlinear optical effect, and chiral-induced spin selectivity have been observed. These unique properties have recently stimulated increasing research interest in circularly polarized light (CPL) detection, circularly polarized photoluminescence and electroluminescence, chiral spintronic devices, etc. Generally speaking, the interdisciplinary chirality and optoelectronics will not only promise new opportunities for fundamental scientific research but also show broad application prospects in 3D display, drug screening, quantum computing and communication, information encryption transmission and processing, etc. In this context, chiral organic optoelectronic materials provide an appealing platform for investigation. In addition to the outstanding optical and electronic properties, chirality can be easily introduced into organic optoelectronic materials via either valence or nonvalence chemistry and can be transferred from the molecular level to the supramolecular, nano/micro, and even macro levels by molecular self-assembly and supramolecular chemistry. Moreover, chiral organic molecules are compatible with most cutting-edge processing techniques, such as vacuum evaporation, spin-coating, blade coating, roll-to-roll, etc., for various types of devices. These optoelectronic devices, including organic solar cells (OSCs), organic field-effect transistors (OFETs), and organic light-emitting diodes (OLEDs), can be manufactured on either rigid or flexible substrate, covering device size from molecular scale (single molecule device) to nano/micro and large area in square meter scale. It is thus worthwhile to review the role of chirality in organic optoelectronic materials and devices to promote further development of chiral organic optoelectronics. In this Account, we intend to showcase the diverse functions empowered by the intriguing properties of chiral organic conjugated molecular assemblies. We will first discuss how chirality affects molecular packing in chiral organic assemblies, from which we will show chirality not only helps elucidate the intermolecular interactions but also impacts hierarchical structures in matters. We then expand the discussion to the interactions between chiral assemblies and guest substances, complicated helical motion, and molecular chirality recognition achieved at nano, micro, or even macro level. We highlight our recent advances in the interactions between chiral assemblies and chiral light. This generates the field of direct CPL detection, and the basic principles in this field will be summed up. Specifically, the underlying mechanism of selective CPL detection by chiral photodiodes and phototransistors, with the principles of down-to-earth optoelectronics, will be addressed. Overall, we outline chiral optoelectronic functional assemblies and devices that provide a promising approach to perceiving chiral entities that are unable to be distinguished by the human senses directly. Finally, we conclude the difficulties and challenges for chiral π-conjugated materials and devices at the present stage and propose perspectives that could be further conducted to boost the chiral optoelectronic materials and devices toward potential applications.