The excitation intensity dependence of singlet fission dynamics of a rubrene microcrystal studied by femtosecond transient microspectroscopy

We have investigated the excitation intensity dependence of the singlet fission in a crystalline rubrene by means of femtosecond transient absorption microspectroscopy. When a rubrene microcrystal was excited to higher energy levels than that of the lowest singlet excited (S1) state with a 397 nm femtosecond laser pulse, a triplet excited state was formed through two pathways of the singlet fission, i.e. the direct fission from higher vibrational levels of the S1 state with a time constant of 2.2 ps and the thermally activated fission from the S1 state in a few tens of ps. The time constant of the thermally activated fission changed from 35 to 17 ps for increasing of the laser fluence from 0.65 to 18 mJ cm-2 per pulse, although that of the direct fission was constant with the excitation laser intensity. On the other hand, the yield of the triplet formation was independent of the intensity. We also examined the temperature dependence of the singlet fission and demonstrated the activation energy of the thermally activated fission to be 0.21 eV. Based on the experimental results, we considered the excitation intensity dependence of the singlet fission of the rubrene crystal in terms of the effect of transient local heating on a ps time scale after femtosecond laser excitation owing to the nonradiative vibrational relaxation from the higher vibrational level to the lower one in the S1 state.

Medienart:

E-Artikel

Erscheinungsjahr:

2016

Erschienen:

2016

Enthalten in:

Zur Gesamtaufnahme - volume:15

Enthalten in:

Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology - 15(2016), 10 vom: 05. Okt., Seite 1304-1309

Sprache:

Englisch

Beteiligte Personen:

Ishibashi, Y [VerfasserIn]
Inoue, Y [VerfasserIn]
Asahi, T [VerfasserIn]

Themen:

Journal Article
Research Support, Non-U.S. Gov't

Anmerkungen:

Date Completed 21.11.2017

Date Revised 28.11.2017

published: Print

Citation Status PubMed-not-MEDLINE

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM265086957