High Efficiency Near-Infrared and Semitransparent Non-Fullerene Acceptor Organic Photovoltaic Cells.

The absence of near-infrared (NIR) solar cells with high open circuit voltage (Voc) and external quantum efficiency (EQE) has impeded progress toward achieving organic photovoltaic (OPV) power conversion efficiency PCE > 15%. Here we report a small energy gap (1.3 eV), chlorinated nonfullerene acceptor-based solar cell with PCE = 11.2 ± 0.4%, short circuit current of 22.5 ± 0.6 mA cm-2, Voc = 0.70 ± 0.01 V and fill factor of 0.71 ± 0.02, which is the highest performance reported to date for NIR single junction OPVs. Importantly, the EQE of this NIR solar cell reaches 75%, between 650 and 850 nm while leaving a transparency window between 400 and 600 nm. The semitransparent OPV using an ultrathin (10 nm) Ag cathode shows PCE = 7.1 ± 0.1%, with an average visible transmittance of 43 ± 2%, Commission d'Eclairage chromaticity coordinates of (0.29, 0.32) and a color rendering index of 91 for simulated AM1.5 illumination transmitted through the cell.