Berlin 2008 – scientific programme

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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 2: Organic Interface Structure and Growth

SYSA 2.6: Talk

Tuesday, February 26, 2008, 12:30–12:45, H 0105

Electronic structure of the CuPc/BPE-PTCDI donor/acceptor hetero interface of organic solar cells for varied O2 and TCNQ doping concentrations — Corinna Hein, •Eric Mankel, Johanna Härter, Thomas Mayer, and Wolfram Jaegermann — Technische Universität Darmstadt, Materials Science Institute, Surface Science Division, Petersenstr. 23, 64287 Darmstadt

The bilayer hetero junction model solar cell of Copper phthalocyanine (CuPc) / BPE-PTCDI, a perylene derivative, shows a low efficiency of 0.8% only. With synchrotron induced photoemission (SXPS) in the course of interface formation we find the development of potential barriers due to band bending, hindering charge collection. To overcome the formation of the barrier we test p-doping of the CuPc layer by oxygen or by TCNQ, which are strong electron acceptors. Oxygen doping of CuPc was performed by evaporation in O2 atmosphere at pressures in the range from 10-8mbar to 10-3mbar which leads to oxygen concentrations less than 1%. A shift of the CuPc Fermi level by 200meV was achieved. TCNQ doping was performed by coevaporation. With increasing TCNQ content in the percent region, a shift of the CuPc Fermi level up to 450meV has been achieved. The doping mechanism has been analyzed by performing SXPS on the TCNQ/CuPc interface. In the course of CuPc deposition we find a shift of the CuPc HOMO by 450 meV indicating electron transfer. In addition an interface dipole of 320 meV is formed.