Pyrene-embedded nanohoops: synthesis and dopant engineering for organic solar cells with an enhanced efficiency of 19.96%

Cycloparaphenylenes (CPPs) have long been a focus of interest for their promising applications in materials science. Herein, we report the synthesis of electron-rich pyrene-embedded nanohoops, [2]OMe-Pyr-[8]CPP and [4]OMe-Pyr-[8]CPP. Single-crystal analysis revealed an oval-shaped cavity with a herringbone molecular packing arrangement, thereby facilitating the formation of extended tubular structures in both derivatives. Photophysical studies revealed that the two pyrene-embedded nanohoops exhibit nearly identical UV-vis absorption and fluorescence emission profiles. We further investigated the potential application of these nanohoops as dopants in organic solar cells (OSCs). When incorporated into D18:L8-BO-based OSCs, [2]OMe-Pyr-[8]CPP enhanced the power conversion efficiency (PCE) from 19.24% to 19.73%. Notably, [4]OMe-Pyr-[8]CPP delivered even better performance, achieving an impressive PCE of 19.96%. These observations indicate that the more electron-rich nanohoop demonstrated superior performance in the present case. These results highlight functionalized CPPs as promising materials for high-performance OSCs, providing an effective strategy for photovoltaic efficiency enhancement.