![]() Only the latter of these excitation wavelengths was sufficient in energy to induce direct one-photon absorption to the singlet excited state in anthracene. 1 Comparison between the fluorescence detected from the anthracene crystals under laser excitation indicated a doubling of triplet generation when switching between the first and second harmonics of the laser source, at 694 and 347 nm, respectively. in 1965, through delayed fluorescence measurements in anthracene crystals. The first experimental observation of this process was by Singh et al. The first period of SF research was focused on spectroscopic studies. ![]() In this review, we compare and categorize these attempts in order to assess the state of the field and identify the most promising avenues of future research and development. Efforts to incorporate this process into solar photovoltaic cells have spanned a wide range of device structures over the past decade. This would potentially allow for efficiency improvements beyond the thermodynamic limit in a single junction cell. Due to this high quantum efficiency, the singlet fission process shows promise as a means of reducing thermalization losses in photovoltaic cells. Since this process is spin-allowed, it can proceed on an ultrafast timescale of less than several picoseconds, outcompeting most other loss mechanisms and reaching quantitative yields approaching 200%. Singlet fission is a form of multiple exciton generation, which occurs in organic chromophores when a high-energy singlet exciton separates into two lower energy triplet excitons, each with approximately half the singlet energy.
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