The structural evolution of an isoindigo-based non-fullerene acceptor for use in organic photovoltaics†
The structural evolution of a functional isoindigo-based non-fullerene acceptor led to the development of three new materials to address the deficiencies of the original framework. Owing to the versatility of the structure and the flexibility of the synthetic procedures, these three new materials were accessible from previously optimized reaction conditions and similar precursor materials. The influence of structural modification on the optical, electrochemical and thermal properties were assessed and correlated with DFT calculations to provide compelling evidence for the effect of each substitution and how they relate to each particular adaptation. The structure–property relationships were investigated for their photovoltaic performance in solution processable BHJ devices fabricated in inverted architectures. Evaluation of device performance demonstrated that a single modification did not improve on the efficiency of the original structure, but the combination of both induced non-planarity, and increased electron affinity of the fourth iteration showed the potential of our framework, with PCE reaching 1.9%.