The seminar will take place at ICMAB - Sala d'Actes MATGAS and Online by Zoom
Conjugated polymer blends coupled by Förster resonance energy transfer (FRET) have been widely exploited to achieve optically-pumped lasers operating at very low pumping thresholds. Among the plaid of conjugated polymers and molecules exploited for optical gain, fluorene-based polymers are considered front-runners, based on their high photoluminescence quantum yields, large optical gain coefficients and their processability assets in films of high optical quality. Two archetypes of polymers with these properties are poly(9,9-dioctyl-fluorene) (PFO) and its green-emitting relative Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) which work as excellent FRET-coupled blends but unexpectedly do not exhibit stimulated emission. In this talk we will shed light into the optical gain limiting factors of these blends.
Upon investigating a series of polyfluorenes bearing different chain length or chain twists, we reveal improvements on the stimulated emission properties by harnessing exciton annihilation. We ascribe these effects to disruption of exciton transport, reducing the yield of charge-transfer states and associated photoinduced absorption losses.
Juan Cabanillas-Gonzalez graduated in Physics at Universidade de Santiago de Compostela in 1999. He got a PhD in Physics from Imperial College London working with photophysics of conjugated polymers with Prof. Donal Bradley. In 2003 he started a post-doctoral stage at Politecnico di Milano with Prof. Guglielmo Lanzani. In 2009 he was appointed Ramon y Cajal fellow at IMDEA Nanociencia (Madrid). Since then he leads his own group at IMDEA Nanociencia.
Hosted by Mariano Campoy-Quiles, NANOPTO group, ICMAB-CSIC