Brominated Perylene Diimides as Cathode Interface Materials for High Efficiency Organic Solar Cells

The cathode interface materials (CIMs) are crucial for organic solar cells (OSCs). Herein, excellent CIMs PDINN‐Br and PDINN‐2Br are reported, by bromination of PDINN. Both of them have strong work function (WF) tunability, self‐doping properties, and excellent film‐forming properties. They show higher electron mobility (over 2 × 10 −4 cm 2 V −1 s −1 ) and conductivity (≈5 × 10 −5 S cm −1 ) than PDINN. Grazing‐incidence wide‐angle X‐ray scattering measurements (GIWAXS) illustrate that PDINN‐2Br has more ordered arrangement than PDINN and PDINN‐Br. PDINN, PDINN‐Br, and PDINN‐2Br in PM6:Y6‐based OSCs lead to 15.96%, 16.71%, and 17.03% power conversion efficiency (PCE), respectively. The PDINN‐2Br has well performance as well in the PM6:PYIT and D18:L8BO OSCs, PCEs of 18.14% and 18.98% are obtained, respectively, which are higher than PDINN (16.97% and 18.01%).