Singlet Fission as an Exciton-Management Platform for Next-Generation Optoelectronic Materials

Singlet fission (SF), the spin-conserving conversion of one photoexcited singlet exciton into two triplet excitons has emerged as a versatile exciton-management strategy for optoelectronics and quantum technologies. While initially explored to overcome the efficiency limit of single-junction photovoltaics, SF is now recognized as a broader platform for engineering correlated excited states. Efficient triplet generation and spin-correlated pairs create opportunities in photovoltaics, photodetection, photocatalysis, photon up-conversion, quantum light sources, spin-photon interfaces, and bioimaging. This Review summarizes the fundamental mechanisms, energetic requirements, and molecular design principles governing SF, together with the influence of supramolecular organization and external stimuli on its dynamics. Particular emphasis is placed on the multiscale relationships among molecular energetics, excited-state character, molecular packing, triplet-pair separation, triplet transport, and interfacial energy or charge transfer, which ultimately determine device performance. We further discuss recent advances in SF-enabled optoelectronic and quantum applications. Despite rapid progress, major challenges remain in establishing a unified mechanistic framework, understanding SF in polymeric and disordered systems, and expanding the library of stable, high-performance SF materials. Finally, we highlight future opportunities in machine-learning-assisted materials discovery, excited-state engineering, and the integration of SF into next-generation functional optoelectronic devices.