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. Efficiency loss in thick film organic solar cells is a bottleneck for scalable manufacturing. Here, the authors present an exciton spin-manipulation strategy to extend exciton diffusion length and reduce non-radiative recombination losses.