Tunable optical and spin properties by fullerene coupling: from an excitonic perspective

In the cluster-assembled hierarchical structures, the quantum confinement and interfacial coupling effects are prominent, offering versatile excitonic and optical properties for both fundamental studies and device applications. Here, we focus on a series of synthetic fullerene complex structures and demonstrate their diverse excitonic characteristics from localized exciton to quadrupolar-like excitons by tuning the inter-cluster coupling. Owing to these unique exciton states, the fullerene complexes exhibit strong fluorescence emission and quantum-confined Stark effect with large Stark shifts, distinct from an isolated fullerene. Moreover, a spin triplet state can be devised to serve as a qubit with spin initialization and readout operating at a wavelength close to the low-loss telecom band. These theoretical results provide a new perspective for manipulating charge, spin, and exciton in the cluster-assembled structures, thereby advancing their applications in light-emitting devices, electro-optic modulation, and quantum information.