Ground‐State Charge‐Transfer Doping in Donor–Acceptor Semiconducting Polymers

Conjugated polymers are at the heart of numerous current and emerging technologies. Doping, a process by which charge carriers are introduced, is crucial to their functionality and performance. Despite a significant historical context, doping processes based on ground‐state charge‐transfer (CT) complex formation, mediated by the supramolecular hybridization between the frontier molecular orbitals of distinct molecular species, remain rare and are consequently poorly understood. In this context, there are no clear demonstrations of this alternative doping phenomenon in contemporary donor–acceptor conjugated polymers. Here, we use diketopyrrolopyrrole‐based donor–acceptor semiconducting polymers and a π ‐conjugated penta‐ t ‐butylpentacyanopentabenzo[25]annulene “cyanostar” macrocycle to demonstrate the first examples of features that control ground‐state CT complex formation in these contemporary conjugated polymer frameworks. Using complementary experimental techniques, we articulate how subtle molecular, electronic, and solid‐state features impact the supramolecular hybridization of the frontier molecular orbitals and impact the resultant (opto)electronic, magnetic, and transport properties. These studies demonstrate that the admixture between distinct π ‐conjugated materials can have dramatic outcomes on solid‐state electronic properties and performance through modification of the density of states. These results and associated mechanistic insight will enable completely new co‐design rules for organic semiconductors and emerging molecular dopants that offer new functionality and precise property control.