Indoor Organic Photovoltaics with Over 29% Efficiency and Great Stability Enabled by Giant Dimeric Acceptors with Hypsochromic Absorption and High Glass Transition Temperature

Abstract Indoor organic photovoltaics (IOPVs) are an emerging LED light recycling technology with promising applications such as indoor off‐grid ecosystem for the Internet of Things. However, efficient and stable IOPVs based on giant dimeric acceptors (GDAs) are rarely reported due to the dearth of GDAs with hypsochromic absorption (absorption onset < 850 nm) and good crystallinity. Herein, two hypsochromic GDAs are proposed with different fluorination degrees, namely DY4FO‐V and DY6FO‐V, and process a systematic study of hypsochromic acceptor materials from the small molecule to dimers and polymer. Interestingly, both hypsochromic GDAs possess better crystallinity, thus faster carrier transport and suppress recombination than small‐molecule and polymer acceptor‐based devices. With extra fluorination, PM6:DY6FO‐V exhibits higher external quantum efficiency response and tighter packing compared with PM6:DY4FO‐V. As a result, PM6:DY6FO‐V delivers a champion efficiency over 29% under a LED illumination of 2000 lux (2600 k), positioning it the highest values for GDA‐based IOPVs. Meanwhile, the high glass transition temperature of DY6FO‐V endowed corresponding devices with great photostability and enhanced mechanical stability in flexible devices, demonstrating the feasibility of practical applications of the DY6FO‐V‐based IOPVs. This research underscores the huge potential of developing hypsochromic GDAs for highly efficient IOPVs with superior stability.