Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 117: Organic semiconductors: Material properties (with CPP/DS)
HL 117.5: Talk
Friday, April 4, 2014, 11:15–11:30, POT 051
Energy-transfer in ZnO/ladder-type oligophenylenes hybrid structures — •Francesco Bianchi1, Sylke Blumstengel1, Fritz Henneberger1, Björn Kobin2, Stefan Hecht2, Raffael Schlesinger1, and Norbert Koch1 — 1Institut für Physik Humboldt-Universität, Berlin, Germany — 2Department of Chemistry Humboldt-Universität, Berlin, Germany
Inorganic/organic hybrid systems designed to inherit the advantageous properties of each of their constituents are of great interest both to basic science as well as for optoelectronic applications. In this regard it is required to find an organic material that exhibits specific properties like narrow transitions, large dipole moment, small emission-absorption Stokes shift and an optical gap that corresponds to the inorganic material. The design we use consists in a three spiro-bridged ladder-type quarter-phenyl (SP3-L4P) grown on ZnO-based single quantum wells (SQW) to obtain incoherent coupling. In such a setting, it should be possible to convert Wannier excitons of the SQW into Frenkel excitons of the organic layer via a Förster type energy transfer (FRET).
We investigate the FRET between SQW with different cap thickness and a 3Sp-L4P thin layer evaporated on top of them. With photoluminescence excitation and time-resolved spectroscopy we demonstrate that these hybrid structures exhibit energy transfer with an efficiency up to 65%. Despite the high efficiency, UPS measurements show a type II interface between ZnO and the molecules layer, leading to a charge separation process that limits the light emitted. Finally we investigate on the use of high gap material spacer to reduce this effect.