Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 62: [DS] Organic Electronics and Photovoltaics I (jointly with CPP, HL, and O)
O 62.4: Vortrag
Donnerstag, 17. März 2011, 11:00–11:15, GER 38
Effect of high-k substrates on the photocurrent of organic semiconductors: Tailoring the Coulomb interaction — •Miriam Engel1, Doru C. Lupascu2, Niels Benson1, and Roland Schmechel1 — 1Nanostrukturtechnik, Universität Duisburg-Essen, 47057 Duisburg — 2Institut für Materialwissenschaft, Universität Duisburg-Essen, 45117 Essen
A major difficulty for organic photovoltaic cells is the dissociation of excitons into free charge-carriers. This is caused by high exciton binding energies, due to the low permittivity of the organic material. There are approaches to use acceptor-donator systems in the form of bulk-heterojunctions, which leads to successful exciton dissociations per volume. However, re-trapping may occur even after efficient charge-carrier separation due to Coulomb interaction (CI). Our aim is to use inorganic high-k materials to increase the exciton dissociation and to lower CI. In our proof of principle experiments devices are based on substrates with different permittivities. Pentacene is deposited as the active organic layer on them. Silver electrodes are used as top-contacts. For the electrical characterization we performed I(V) measurements in the dark and under illumination. Because of the known influence of the pentacene morphology on the mobility of the charge-carriers, we corrected the current under illumination by the dark current to obtain the pure contribution from the photo-effect. We obtained an improvement of the photocurrent using high-k substrates. The final goal is to transfer the layered system into an organic-inorganic composite system with high-k nanoparticles embedded in a photoactive organic matrix.