Enhancing the Performance of Polymer Solar Cells via Core Engineering of NIR‐Absorbing Electron Acceptors

In order to utilize the near‐infrared (NIR) solar photons like silicon‐based solar cells, extensive research efforts have been devoted to the development of organic donor and acceptor materials with strong NIR absorption. However, single‐junction organic solar cells (OSCs) with photoresponse extending into >1000 nm and power conversion efficiency (PCE) >11% have rarely been reported. Herein, three fused‐ring electron acceptors with varying core size are reported. These three molecules exhibit strong absorption from 600 to 1000 nm and high electron mobility (>1 × 10−3 cm2 V−1 s−1). It is proposed that core engineering is a promising approach to elevate energy levels, enhance absorption and electron mobility, and finally achieve high device performance. This approach can maximize both short‐circuit current density ( JSC) and open‐circuit voltage (VOC) at the same time, differing from the commonly used end group engineering that is generally unable to realize simultaneous enhancement in both VOC and JSC. Finally, the single‐junction OSCs based on these acceptors in combination with the widely polymer donor PTB7‐Th yield JSC as high as 26.00 mA cm−2 and PCE as high as 12.3%. Single‐junction binary‐blend polymer solar cells based on PTB7‐Th/F8IC afford efficiency of 10.9%, which is higher than those of F6IC (7.1%) and F10IC (10.2%) counterparts. Furthermore, ternary‐blend devices based on PTB7‐Th/F8IC/PC71BM exhibit JSC as high as 26.00 mA cm−2 and power conversion efficiency as high as 12.3%.