Applying hydrostatic pressure as an external stimulus, Tokyo Tech and Keio University researchers demonstrate a new way to regulate singlet fission (SF), a process in which two electrons are generated from a single photon, in chromophores, opening doors to the design of SF-based materials with enhanced (photo)energy conversion. Their method overrides the strict requirements that limit the molecular design of such materials by realizing an alternative control strategy.
Singlet fission (SF) is a process in which an organic chromophore (a molecule that absorbs light) in an excited singlet state transfers energy to a neighboring chromophore, resulting in two correlated triplet exciton pairs (pairs of bound electron-hole states, a "hole" signifying the absence of an electron) that decay to low energy triplet excitons. These excitons have long lifetimes and show efficient light emission, making SF promising for efficient light energy conversion.
However, the molecular design of SF-based materials is limited by the requirement that the energy of the excited singlet state must be at least equal to the energy of the two triplet states. One way to overcome this limit is by applying external stimuli, such as temperature or pressure, to manipulate the SF process.