Recent Progress in π-Conjugated Polymers for Organic Photovoltaics: Solar Cells and Photodetectors

π-Conjugated polymers show promising potential in the application of organic photovoltaics, including organic solar cells (OSCs) and organic photodetectors (OPDs) because of merits of light-weight, flexibility, facilely tuned color, large-scaled solution-processability, etc. Over the past three decades, various π-conjugated polymers have been developed owing to the continuous efforts of researchers, which significantly promote the OPVs technology to an unprecedented stage. In order to reveal the relationship among polymer structures to the optical and electronic properties and interchain aggregation and morphology and finally to device performance, it is of great significance to review the progress of π-conjugated polymers for OPVs, particularly for outstanding achievements in recent all-polymer solar cells (all-PSCs), indoor organic photovoltaics (IOPVs), thick-film OSCs, single-component organic solar cells (SCOSCs) and short-wave infrared (SWIR) OPDs. This review highlights general design strategies of π-conjugated polymers for high-performance OPVs, including conjugated backbone engineering, side-chains engineering, regioregularity engineering, halogen substitution and molecular weight control. Then, the development of conjugated polymers for all-PSCs, IOPVs, thick-film OSCs, SCOSCs and OPDs has been summarized. At the end, we summarize the challenges and future directions for studying π-conjugated polymers for OPVs. Therefore, an in-depth understanding of designing π-conjugated polymers is speculated to advance the development of current OPV materials and thus accelerate the ultimate industrialization of the OPV technology.