From single molecule to molecular aggregation science

For the organic opto-electronic materials, the macroscopic performance of molecular aggregates is not just the simple overlay of single molecules, and in many cases, new properties can be generated by molecular uniting with particular packing modes, which are mainly determined by molecular structures of organic compounds. This review takes the photophysical properties as the key point, mainly discussing the regulation of molecular aggregation to improve and generate the interestingly luminescent properties. Among them, mechanoluminescence (ML) and room-temperature phosphorescence (RTP) are emphasized as the typical emission property sensitive to molecular aggregates. Also, the dynamic photophysical properties with the tiny variations in molecular motions and/or packing modes by various external stimuli are highlighted to investigate the possible relationship between opto-electronic performance and aggregated structures. Accordingly, the adjustable molecular packing in different fields is discussed in detail, including the internal mechanism, main effective factors, control methods, and preferred structures in various functional materials, with the aim to afford the guideline to molecular design of organic opto-electronic materials, and promote their development from the internal to external.