Near‐Infrared Materials: The Turning Point of Organic Photovoltaics

Abstract Near‐infrared (NIR)‐absorbing organic semiconductors have opened up many exciting opportunities for organic photovoltaic (OPV) research. For example, new chemistries and synthetical methodologies have been developed; especially, the breakthrough Y‐series acceptors, originally invented by our group, specifically Y1, Y3, and Y6, have contributed immensely to boosting single‐junction solar cell efficiency to around 19%; novel device architectures such as tandem and transparent organic photovoltaics have been realized. The concept of NIR donors/acceptors thus becomes a turning point in the OPV field. Here, the development of NIR‐absorbing materials for OPVs is reviewed. According to the low‐energy absorption window, here, NIR photovoltaic materials (p‐type (polymers) and n‐type (fullerene and nonfullerene)) are classified into four categories: 700–800 nm, 800–900 nm, 900–1000 nm, and greater than 1000 nm. Each subsection covers the design, synthesis, and utilization of various types of donor (D) and acceptor (A) units. The structure–property relationship between various kinds of D, A units and absorption window are constructed to satisfy requirements for different applications. Subsequently, a variety of applications realized by NIR materials, including transparent OPVs, tandem OPVs, photodetectors, are presented. Finally, challenges and future development of novel NIR materials for the next‐generation organic photovoltaics and beyond are discussed.