To fully utilize singlet fission as an exciton multiplication pathway in optoelectronic devices, it is essential to understand and control the separation and diffusion of triplet excitons. In exoergic singlet fission materials like pentacenes, triplet transport requires direct wavefunction overlap because triplet transfer involves a spin-forbidden de-excitation step. Combining ultrafast spectroscopy with quantitative structural characterization of crystalline TIPS-Pn films allows us to elucidate the mechanism of correlated triplet pair (CTP) separation following ultrafast singlet fission of photogenerated singlet excitons. We use triplet annihilation kinetics to quantify changes in triplet diffusivity with crystalline structure and morphology. Whole pattern fitting of X-ray diffraction patterns combined with quantum chemical calculations reveal the correlation of triplet transfer rates with the underlying crystalline packing geometries. Ultrafast measurements of CTP separation on the picosecond time scale demonstrates that this process shares the same underlying dependence on crystalline packing arrangements as does triplet exciton diffusion – triplet transfer.

Mechanisms of triplet pair separation and transport following singlet fission in functionalized pentacenes

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.