Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 67: Organic Semiconductors: Solar Cells II (Joint Session with DS/CPP/O)

HL 67.1: Talk

Friday, March 26, 2010, 10:15–10:30, H16

Organic-inorganic heterojunction with P3HT and n-type 6H-SiC: Determination of the band alignment and photovoltaic properties — •Roland Dietmüller, Helmut Nesswetter, Sebastian Schöll, Benedikt Hauer, Ian David Sharp, and Martin Stutzmann — Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany

The exact band alignment in organic/inorganic semiconductor heterojunctions is influenced by a variety of properties and difficult to predict. For the organic/inorganic heterojunction made of poly(3-hexylthiophene) (P3HT) and n-type 6H-SiC, the band alignment is determined via current-voltage measurements. For this purpose a model equivalent circuit, combining a thermionic emission diode and space-charge limited current effects, is proposed which describes the behavior of the heterojunction very well. From the fitting parameters, the interface barrier height of 1.1 eV between the lowest unoccupied molecular orbital (LUMO) of P3HT and the Fermi level of 6H-SiC can be determined. In addition from the maximum open circuit voltage of the diodes, a distance of 0.9 eV between the HOMO of P3HT and the conduction band (CB) of 6H-SiC can be deduced. These two values determine the Fermi level of 6H-SiC, which is about 120 meV below the CB, relative to the HOMO and LUMO of P3HT. The 6H-SiC/P3HT heterojunction exhibits an open circuit voltage of 0.55 eV at room temperature, which would make such a heterojunction a promising candidate for bulk heterojunction hybrid solar cells with 6H-SiC nanoparticles.