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Bridgehead imine-substituted cyclopentadithiophene structural units, in combination with highly electronegative acceptors that exhibit progressively delocalized π-systems, afford donor-acceptor (DA) conjugated polymers with broad absorption profiles that span technologically relevant wavelength (λ) ranges from 0.7 < λ < 3.2 μm. A joint theoretical and experimental study demonstrates that the presence of the cross-conjugated substituent at the donor bridgehead position results in the capability to fine-tune structural and electronic properties so as to achieve very narrow optical bandgaps ( Egopt < 0.5 eV). This strategy affords modular DA copolymers with broad- and long-wavelength light absorption in the infrared and materials with some of the narrowest bandgaps reported to date. [ABSTRACT FROM AUTHOR]

Front Cover: Bridgehead imine ‐ substituted cyclopentadithiophene structural units, in combination with strong acceptors with progressively delocalized π ‐ systems, afford modular donor ‐ acceptor copolymers with broad and long wavelength light absorption in the infrared. These solution ‐ processable materials possess some of the narrowest bandgaps reported to date and elucidate important aspects of the role of chemical structure in controlling the primary photoexcitations in conjugated copolymer systems. Further details can be found in the article by M. E. Foster, B. A. Zhang, D. Murtagh, Y. Liu, M. Y. Sfeir, B. M. Wong, and J. D. Azoulay* on page 1516. [ABSTRACT FROM AUTHOR]