Regulating Crystallinity of Dimeric Acceptors via Central Core Engineering for Efficient Ternary Organic Solar Cells

Abstract

Controlling the crystallization behavior of the active layer is essential for optimizing the photovoltaic performance of ternary organic solar cells (TOSCs). Precisely tuning crystallinity is a key strategy to improve power conversion efficiency (PCE). To elucidate the impact of dimeric acceptor crystallinity on active layer morphology and charge transport properties, two new dimeric non-fullerene acceptors with extended π-conjugation, S-EDOT and Se-EDOT, were synthesized. Se-EDOT exhibits higher crystallinity due to selenium incorporation. Introducing S-EDOT or Se-EDOT as a third component into the PM6:BTP-4Cl blend film resulted in a significant enhancement in device performance. Notably, the moderate crystallinity of S-EDOT facilitated the formation of an ordered charge transport network, effectively suppressing trap-state density and improving charge carrier mobility, ultimately achieving a maximum PCE of 18.29% in the PM6:BTP-4Cl:S-EDOT ternary device. These findings highlight the crucial role of precisely modulating the crystallinity of the third component to optimize morphology and charge transport characteristics in TOSCs. Moreover, dimeric acceptors with moderate crystallinity demonstrate advantages in optimizing phase separation and charge transport, providing valuable design principles for high performance ternary organic photovoltaics.