Spin-manipulation via novel MoPS₃ nanocrystal for high-performance thick-film organic solar cells

The realization of high-efficiency thick-film organic solar cells (OSCs) is crucial for scalable manufacturing yet remains challenging due to limited exciton diffusion. Here, we introduce a magnetic strategy by incorporating two-dimensional (2D) ferromagnetic MoPS₃ nanocrystal into the active layer to manipulate exciton spin dynamics. We demonstrate that the interaction between the ferromagnetic MoPS₃ nanocrystal and excitons promotes the formation of weak intrinsic magnetic fields within the active layer. These fields effectively promote the intersystem crossing (ISC) from short-lived singlet excitons to long-lived triplet excitons, thereby extending exciton diffusion length and reducing non-radiative recombination losses. Consequently, MoPS₃ nanocrystal doped D18-Cl:L8-BO devices achieve power conversion efficiencies of 20.37% at an active layer thickness of 100 nm and 19.36% (19.13% certified value) at an active layer thickness of 300 nm, representing one of the highest reported values for thick-film ( > 300 nm) OSCs. Universal applicability is demonstrated with power conversion efficiencies of 20.91%/19.63% (D18:L8-BO) and 19.13%/17.92% (PM6:Y6) at 100/300 nm. This work establishes 2D ferromagnetic MoPS₃ nanocrystal as effective spin manipulators in organic semiconductors and provides a universal strategy to overcome the critical thickness-performance trade-off in OSCs.