Intrinsic Advantage of Fused-Ring Nonfullerene Acceptor-Based Organic Solar Cells to Reduce Voltage Loss

The large voltage loss is a significant disadvantage of organic solar cells (OSCs) compared with inorganic and perovskite solar cells and should be reduced to further improve the power conversion efficiency of OSCs. Herein, the voltage loss in OSCs with a systematically controlled energy difference between the excited and charge transfer states is discussed. The voltage loss is compared between two types of OSCs: narrow-bandgap donors paired with wide-bandgap acceptors and narrow-bandgap fused-ring nonfullerene acceptors (NFAs) paired with wide-bandgap donors, to elucidate whether there are any essential advantages in the latter. The first advantage of narrow-bandgap-NFA-based OSCs is their higher photoluminescence quantum yield, owing to their rigid fused-ring architecture. The second advantage is the ability to achieve efficient charge separation with a small voltage loss.