Exploration of Porphyrin-based Semiconductors for Negative Charge Transport Applications Using Synthetic, Spectroscopic, Potentiometric, Magnetic Resonance, and Computational Methods

The development of organic semiconductors that favor electrons as the majority carriers (n-type) lags behind the advances in hole transporting (p-type) materials. This shortcoming suggests that the design space for n-type materials is not yet well explored.An approach is described that adapts meso-to-meso ethyne-bridged porphyrin arrays to n-type applications. Vis-NIR spectroscopic and magnetic resonance measurements are presented that reveal the vastest electron-polarons ever observed in a ¿-conjugated material, underscoring the aptitude for these porphyrin arrays to delocalize negative charge due to miniscule electron-lattice couplings. Also described is the development of an ethyne-bridged porphyrin-isoindigo chromophore that can take the place of fullerenes in conventional thin film solar cell architectures. Particularly noteworthy is the use of a 5,15-bis(heptafluoropropyl)porphyrin building block to engineer a chromophore that, gram for gram, is twice as absorptive as poly(3-hexyl)thiophene and yet possesses a photoexcited singlet state sufficiently energetic to transfer a hole to this polymer. Finally, synthetic efforts are presented that expand the repertoire of available meso-heptafluoropropyl porphyrin building blocks. The findings suggest that the remaining challenges to the exploitation of these pigments will be overcome using a firm grasp of their subtle electronic structures and a willingness to eschew customary strategies for chromophore assembly.