Breaking charge conjugation symmetry for novel π-conjugated donor and acceptor materials design

Seeking for novel π-conjugated electron-donating materials with targeted optical bandgaps and novel electron-accepting materials with compatible orbital alignments is not only a grand scientific challenge, but also in great practical needs for systematically improving the performance of organic optoelectronic devices. In this work, we will present the first combinatorial bandgap design map over 780 different copolymer donor materials with their targeted optical bandgap values effectively covering the entire solar spectrum from the infrared, visible, to ultraviolet regions. Novel electron acceptor materials are constructed with full flexibility in both the orbital alignments and functional side-group additions beyond the commonly used fullerene-based structures. All of these new materials designs are made possible through breaking the charge conjugation symmetry (CCS) in the underlying electron-phonon couplings that are intrinsic to these π-conjugated systems. Combined with empirical arguments widely acknowledged in the literature, new π-conjugated structures are identified with the optimal power conversion efficiencies for both single- and tandem-cells.