An Electron-Deficient Building Block Based on the B←N Unit: An Electron Acceptor for All-Polymer Solar Cells

A double B←N bridged bipyridyl (BNBP) is a novel electron‐deficient building block for polymer electron acceptors in all‐polymer solar cells. The B←N bridging units endow BNBP with fixed planar configuration and low‐lying LUMO/HOMO energy levels. As a result, the polymer based on BNBP units (P‐BNBP‐T) exhibits high electron mobility, low‐lying LUMO/HOMO energy levels, and strong absorbance in the visible region, which is desirable for polymer electron acceptors. Preliminary all‐polymer solar cell (all‐PSC) devices with P‐BNBP‐T as the electron acceptor and PTB7 as the electron donor exhibit a power conversion efficiency (PCE) of 3.38 %, which is among the highest values of all‐PSCs with PTB7 as the electron donor. A bridge too far: An electron‐deficient building block comprises a double B←N bridged bipyridyl (BNBP) moiety. The polymer constructed from the BNBP units exhibits high electron mobility, low‐lying LUMO/HOMO energy levels, and strong absorbance in the visible range, and shows excellent device performance as polymer electron acceptor for all‐polymer solar cells.