Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 41: Organic Photovoltaics III

CPP 41.5: Talk

Friday, March 27, 2009, 11:30–11:45, ZEU 222

Doping of organic absorbers for application in solar cells — •Corinna Hein, Eric Mankel, Thomas Mayer, and Wolfram Jaegermann — Technische Universität Darmstadt, Materials Science Institute, Surface Science Division, 64287 Darmstadt, Germany

The band alignment of the absorbing layers of an organic bilayer heterojunction solar cell was determined by synchrotron induced photoemission (SXPS). As donor type material copper phthalocyanine (CuPc) was used, the acceptor layer consists of BPE-PTCDI (a perylene derivate). At the CuPc/BPE-PTCDI interface a band bending is induced that retains the generated charge carriers leading to recombination and a low photo current of 2.4 mA/cm2. P-doping is suggested to reverse the electric field. As dopant WO3 was used, known to be a strong electron acceptor. Doping was successfully performed by coevaporation of the CuPc matrix and the dopant showing high doping efficiency and limit. The Fermi level shifts gradually with the concentration of dopant up to 690 meV. The doping mechanism was additionally investigated by layer by layer photoemission studies. Assuming phase separation the doping limit can be explained by an interface dipole. Using the doped CuPc the field at the bilayer heterojunction was reversed to the beneficial direction.