Superlinear density dependence of singlet fission rate in tetracene films

TL;DR

This study demonstrates that the singlet fission rate in tetracene films increases superlinearly with exciton density, suggesting a possible coherent process involving superradiant excitons, which could clarify existing debates.

Contribution

It provides experimental evidence of superlinear density dependence of singlet fission rate and proposes a coherent exciton mechanism in tetracene films.

Findings

Superlinear density dependence of singlet fission rate.

Disentanglement of singlet and triplet dynamics using SVD.

Hypothesis of coherent singlet fission involving superradiant excitons.

Abstract

We experimentally show that the rate of singlet fission in tetracene films has a superlinear dependence on the density of photo-excited singlet excitons with ultrafast transient absorption spectroscopy. The spectrotemporal features of singlet and triplet dynamics can be disentangled from experimental data with the algorithm of singular value decomposition. The correlation between their temporal dynamics indicates a nonlinear density dependence of fission rate, which leads to a conjecture of coherent singlet fission process arising from superradiant excitons in crystalline tetracene. This hypothesis might be able to resolve some long-standing controversies.