Berlin 2015 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: Organic Electronics and Photovoltaics: Transport of Charges - from Molecules to Devices (joint session with HL, TT)
CPP 16.2: Talk
Tuesday, March 17, 2015, 09:45–10:00, C 130
Dimensionality of excitation transport in sol-gel-derived polymeric carbon nitride photocatalysts — •Christoph Merschjann1,2, Stefanie Tschierlei1, Kamalakannan Kailasam3, Arne Thomas3, Dirk Hollmann4, and Stefan Lochbrunner1 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Freie Universität Berlin, D-14195 Berlin, Germany — 3Leibniz-Institut für Katalyse, D-18059 Rostock, Germany — 4Technische Universität Berlin, D-10623 Berlin, Germany
The spectral and temporal development of optically excited states in highly active sol-gel-derived polymeric carbon nitride (SG-CN) photocatalysts is investigated using time-resolved optical spectroscopy. By combining transient absorption results from a femtosecond pump-probe setup and transient photoluminescence using streak-camera investigations, the evolution of a light-emitting species appearing upon UV excitation is obtained. The emission decay reveals a universal power-law behaviour over more than seven decades in time (150 fs to 5 µs), the main difference between samples being the characteristic decay time in the nanosecond range. This finding is consistently described using a random-walk approach for the diffusive transport of light-induced polaron pairs, including both geminate and bimolecular recombination mechanisms. Thus, important features of the light-induced charge transport, namely the dimensionality and the regime of reasonable carrier mobilities, are deduced.
The validity of the approach is shown via comparison to ESR-based carrier-density measurements and photocatalytic activities.