Low‐Bandgap Porphyrins for Highly Efficient Organic Solar Cells: Materials, Morphology, and Applications

Abstract With developments in materials, thin‐film processing, fine‐tuning of morphology, and optimization of device fabrication, the performance of organic solar cells (OSCs) has improved markedly in recent years. Designing low‐bandgap materials has been a focus in order to maximize solar energy conversion. However, there are only a few successful low‐bandgap donor materials developed with near‐infrared (NIR) absorption that are well matched to the existing efficient acceptors. Porphyrin has shown great potential as a useful building block for constructing low‐bandgap donor materials due to its large conjugated plane and strong absorption. Porphyrin‐based donor materials have been shown to contribute to many record‐high device efficiencies in small molecule, tandem, ternary, flexible, and OSC/perovskite hybrid solar cells. Specifically, non‐fullerene small‐molecule solar cells have recently shown a high power conversion efficiency of 12% using low‐bandgap porphyrin. All these have validated the great potential of porphyrin derivatives as effective donor materials and made DPPEZnP‐TRs a family of best low‐bandgap donor materials in the OSC field so far. Here, recent progress in the rational design, morphology, dynamics, and multi‐functional applications starting from 2015 will be highlighted to deepen understanding of the structure–property relationship. Finally, some future directions of porphyrin‐based OSCs are presented.