Synthesis of an immobilizable p-dopant and covalent binding onto a polymeric semiconductor

We report the covalent immobilization of a state-of-the-art p-type dopant, azido-functional radialene-based CN5HexN3-CP (6-azidohexyl-2-(2,3-bis(dicyanomethylene)-cyclopropylidene)-2-cyanoacetate) onto alkyne-functionalized carbazole polymers, representing, to our knowledge, the first demonstration of covalent binding of a high-oxidizing p-dopant. The dopant salts (CN5HexN3-CP-2Na and CN5HexN3-CP-2TBA) were attached via thermal Huisgen cycloaddition and copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, allowing precise control over the dopant fraction, which was confirmed by NMR spectroscopy. Due to the extreme reactivity of the neutral dopant, direct immobilization in its active state is not feasible, therefore the dopant was introduced on the polymer backbone in its reduced, inert form. Cyclic voltammetry demonstrated that the immobilized dopant retains its intrinsic redox properties, while polymer backbone doping is prevented by the energy level mismatch. External oxidation experiments confirm the feasibility of ion exchange and formation of partial charge-transfer interactions, providing a proof-of-concept for covalent dopant immobilization. Conceptually, this work addresses a fundamental challenge in organic electronics: the creation of stable multilayer doping profiles as a prerequisite for organic p/n junctions. By immobilizing both dopant and polymer matrix, counterion migration is suppressed, providing a chemically defined framework for localized charge stabilization. • We report the first covalent immobilization of a high-oxidizing p-type dopant onto a polymer semiconductor, • It is relying on a post-immobilization activation strategy that preserves its redox activity. • This approach provides a chemically defined framework for stable charge localization, representing a crucial step toward the realization of organic p/n junctions.