Access to sensitive near infrared circularly polarized light detection via non-fullerene acceptor blends

Circularly polarized light (CPL), as a light source, offers greater light persistence than both non-polarized light and linearly polarized light, and is widely used for high-contrast sensing technologies. An everlasting challenge in realizing full-spectrum CPL detection when using chiral organic semiconductors is to achieve strong chiroptical activities in the near infrared (NIR) region. The conventional approaches to reducing the band gap of organic semiconductors are based on co-planar backbones and lead to molecular symmetries incompatible with the presence of chirality; thus, the strategies to design chiral molecules rely on twisted stereogenic moieties. Here, instead of a de novo design of chiral molecular structures, we introduce a widely applicable strategy to directly induce chiroptical activity in planar non-fullerene acceptors (NFAs), which have been largely developed in the framework of organic photovoltaics and provide a wealth of opportunities to fill the spectral gap of CPL detection in the NIR. We demonstrate proof-of-concept circularly polarized organic photodiodes (CP-OPDs) using chiroptically active NFA blends, which exhibit strong circular dichroism (CD) and hence great sensitivity to CPL in the NIR region. Importantly, this strategy is found to be effective in a wide series of state-of-the-art NFA families, i.e., ITIC, o-IDTBR, and Y6 analogs, which significantly broadens the range of materials applicable to NIR CPL detection and can inspire further designs of strongly CPL-active systems for chiropto-electronics.