13.9% Efficiency Ternary Nonfullerene Organic Solar Cells Featuring Low-Structural Order

The insufficient phase separation between polymer donors and nonfullerene acceptors (NFAs) featuring low structural order disrupts efficient charge transport and increases charge recombination, consequently limiting the maximum achievable power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, an NFA IT-M has been added as the third component into the PBDB-T: m -INPOIC OSCs and is shown to effectively tune the phase separation between donor and acceptor molecules, although all components in the ternary system exhibit low degrees of structural order. The incorporation of 10 wt % IT-M into a PBDB-T: m -INPOIC binary host blend appreciably increases the length scale of phase separation, creating continuous pathways that increase and balance charge transport. This leads to an enhanced photovoltaic performance from 12.8% in the binary cell to 13.9% for the ternary cell with simultaneously improved open-circuit voltage, short-circuit current, and fill factor. This work highlights the beneficial role of ternary components in controlling the morphology of the active layer for high-performance OSCs.