Ternary Strategy for Energy Loss Suppression toward Efficient Rigid and Flexible Organic Solar Cells

Abstract

Minimizing energy loss is critical for enhancing the efficiency of organic solar cells (OSCs), particularly for flexible applications where the voltage loss tends to be more severe. In this work, we demonstrate a high-efficiency ternary OSC by incorporating a non-fullerene small molecule, ZY-4Cl, into the PM6:L8-BO binary blend. The introduction of ZY-4Cl extends the absorption window and establishes a favorable energy cascade with PM6 and L8-BO. Furthermore, ZY-4Cl mitigates trap states and improves film morphology, which collectively suppress charge recombination and enhance the open-circuit voltage (Voc) of OSCs. The ternary system also exhibits reduced energetic disorder and lower non-radiative recombination loss, as confirmed by a series of spectroscopic and transient characterizations. As a result, the optimized ternary device achieves an efficiency of 19.90% with a significantly elevated Voc. Notably, the ternary strategy is successfully applied to flexible substrates, yielding a high efficiency of 18.51%, which is among the highest values reported for flexible OSCs, while maintaining superior voltage output. This study highlights the synergistic benefits of ternary blend engineering for simultaneously improving Voc, short-circuit current (Jsc), and fill factor (FF), offering new insights into energy loss reduction and advancing the practical deployment of high-performance rigid and flexible OSCs.