An Optical Power Limiting and Ultrafast Photophysics Investigation of a Series of Multi-Branched Heavy Atom Substituted Fluorene Molecules Article - Octobre 2019

Hampus Lundén, Delphine Pitrat, Jean-Christophe Mulatier, Cyrille Monnereau, Iulia Minda, Adrien Liotta, Pavel Chábera, Didrik Hopen, Cesar Lopes, Stéphane Parola, Tönu Pullerits, Chantal Andraud, Mikael Lindgren

Hampus Lundén, Delphine Pitrat, Jean-Christophe Mulatier, Cyrille Monnereau, Iulia Minda, Adrien Liotta, Pavel Chábera, Didrik Hopen, Cesar Lopes, Stéphane Parola, Tönu Pullerits, Chantal Andraud, Mikael Lindgren, « An Optical Power Limiting and Ultrafast Photophysics Investigation of a Series of Multi-Branched Heavy Atom Substituted Fluorene Molecules  », Inorganics, octobre 2019, p. 126. ISSN 2304-6740

Abstract

A common molecular design paradigm for optical power limiting (OPL) applications is to introduce heavy atoms that promote intersystem crossing and triplet excited states. In order to investigate this effect, three multi-branched fluorene molecules were prepared where the central moiety was either an organic benzene unit, para-dibromobenzene, or a platinum(II)–alkynyl unit. All three molecules showed good nanosecond OPL performance in solution. However, only the dibromobenzene and Pt–alkynyl compounds showed strong microsecond triplet excited state absorption (ESA). To investigate the photophysical cause of the OPL, especially for the fully organic molecule, photokinetic measurements including ultrafast pump–probe spectroscopy were performed. At nanosecond timescales, the ESA of the organic molecule was larger than the two with intersystem crossing (ISC) promoters, explaining its good OPL performance. This points to a design strategy where the singlet-state ESA is balanced with the ISC rate to increase OPL performance at the beginning of a nanosecond pulse.

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