Efficient DPP Donor and Nonfullerene Acceptor Organic Solar Cells with High Photon-to-Current Ratio and Low Energetic Loss

The high crystallinity and ability to harvest near-infrared photons make diketopyrrolopyrrole (DPP)-based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP-based OSC devices still suffer from the trade-off between energetic loss (E-loss) and maximum external quantum efficiency (EQE(max)), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP-donor-based solar cells due to severe charge recombination issues. In this work, efficient DPP-based solar cells are reported using low bandgap fused ring electron acceptor, IEICO-4F. PBDTT-DPP:IEICO-4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low E-loss of 0.57 eV and a high EQE(max) (>70%).