Enabling High‐Efficiency and Stable Binary Organic Solar Cells by Solid Additive‐Assisted Morphology Modulation

Abstract The solid additive strategy represents a simple yet effective approach to achieving high‐efficiency organic solar cells (OSCs) by enhancing the morphology of the active layer. In this study, a highly volatile solid additive, 2,4,6‐trichloro‐1,3,5‐triazine (TCT), is employed to modulate the morphology. Unlike other solid additives previously reported, TCT exhibits remarkable intermolecular interactions with both polymer donor and acceptor, offering two distinct advantages. Firstly, TCT notably enhances the crystallinity and molecular order of the blend film, subtly optimizing the fiber network structure within, thereby facilitating carrier transport and significantly improving the mobility of the blend film. Secondly, TCT stabilizes the bi‐continuous fibrous morphology of the polymer donor and acceptor, mitigating the morphological evolution of the active layer and enhancing device stability. Consequently, the D18:L8‐BO:TCT device exhibits a higher power conversion efficiency of 19.50% compared to the D18:L8‐BO device (18.13%). Furthermore, after 960 h of storage, the OSC device treated with TCT retains 90% of its initial PCE, significantly outperforming the D18:L8‐BO device (73%). This study presents a promising avenue for achieving high‐performance OSCs through manipulating the active layer morphology with solid additives.