Decoding Nucleation and Growth in Organic Semiconductor Films

The nucleation of ƒÎ]conjugated molecules and polymers, whether in solution, at elevated temperatures, or with the use of processing additives, dictates the relative degrees of order in organic semiconductor films. While general underpinnings have been set to direct molecular packing in thin films through molecular and processing design, there currently exist no stead]fast rules to control order over the many length scales of an organic semiconducting film. This is in part due to the lack of understanding of nucleation itself, including the interplay between conformational and configurational entropy, and how the relatively complex nature of these ƒÎ]conjugated systems are manifest in nucleation. Here we aim to provide a general understanding of nucleation in ƒÎ]conjugated systems of interest for organic solar cell applications. To accomplish this goal, we set forth three objectives: (i) determine how the structural rigidity of ƒÎ]conjugated polymers controls aggregation in solution; (ii) explore how the nature of alkyl chains appended to ƒÎ]conjugated backbones impact the initial formation nucleates; and (iii) develop a general physical model that lays bare the relationships between conformational and configurational entropy and the kinetics of nucleate formation in order to control disorder during the formation of organic semiconducting films. Given the vast utility of ƒÎ]conjugated molecules and polymers across a range of technologies . including field]effect transistors, light]emitting diodes, supercapacitors, batteries, bioelectronics, electrochromics . and the similar structural components to materials systems used in technologies such as antibiofouling, it is expected that the results of this program will have wide]ranging consequence.