Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 58: Focus Session: Structure and Transport in Organic Photovoltaics III (jointly with CPP)
HL 58.2: Vortrag
Mittwoch, 28. März 2012, 15:15–15:30, ER 270
Transport and Electric Fields in Amorphous Silicon Organic Hybrid Solar Cells — •Sebastian Schaefer1, Tim Schulze2, Lars Korte2, Aad Gordijn3, Jan Wördenweber3, and Dieter Neher1 — 1Universität Potsdam, Germany — 2Helmholtz Zentrum Berlin, Germany — 3Forschungszentrum Jülich GmbH, Germany
We investigated hybrid structures based on nip a-Si:H cells where the p-type layer is replaced by the low band gap polymer PCPDTBT. In these devices the polymer acts as an extraction layer for holes generated in the intrinsic a-Si:H layer and additionally generates charge carriers in the red part of the spectrum, where a-Si:H does not absorb. IV- and quantum efficiency measurements of the hybrid cell show that both materials contribute to the photocurrent generation, indicating that exciton splitting at the hybrid interface as well as hole transfer from a-Si:H to the polymer are provided by the structure. However, low short circuit currents and fill factors lead to poor efficiencies. Simulations of the hybrid device band structure with AFORS-HET (Automat for Simulation of Heterostructures, Helmholtz Zentrum Berlin) indicate that low electric fields in the amorphous silicon layer may lead to the limited performance. This turns out to be a general problem of hybrid inorganic-organic devices since the dielectric constants differ remarkably between these materials. We investigated the electric fields in the hybrid cell with electroabsorption measurements which support our theoretical assumptions. Further studies show that by using doped organic layers the electric field is reconditioned in the amorphous silicon, leading to much better device performance.