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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.85: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Long term aging behavior of ZnPc:C60 Organic Solar Cells under controlled conditions — •Rudolf Lessmann¹, Ziruo Hong², Moritz K. Riede¹, and Karl Leo¹ — ¹IAPP - Institut Für Angewandte Photophysik, Technische Uniservität Dresden, Germany — ²Department of Materials Science & Engineering, University of California, Los Angeles, USA

Cu or Zn Phtalocyanines (CuPc and ZnPc) and C60 are frequently used for organic solar cells, since their energy levels form a donor-acceptor hetero junction and they have high absorption coefficients and a complementary absorption in the sun spectrum. Its known from literature that strong degradation is induced by oxygen diffusion in C60 wich acts as an exciton quencher, drastically reduces the mobility, and eventually decomposes C60. Here, we analyze the long term aging behavior of solar cells based on flat and bulk ZnPc/C60 heterojunctions under controlled conditions. The starting structure is ITO(120 nm)/ZnPc(15 nm)/C60(40 nm)/buffer(4 nm)/Al(100 nm). Devices encapsulated with glass and UV epoxy were aged under controlled temperature and illumination at 475 nm (intensities > 10 mW/cm²), corresponding to the maximum photo-response of C60 in the visible spectra for this device structure. We experimentally address new ways to stabilize the C60 - oxygen interaction in the device. The overall degradation is quite fast, the fitted time to half of initial value (t_H) of I_SC is on the order of 1000 h. After that time I(−1V) is still around 95% of its initial value, indicating that the degradation is mainly driven by changes of the transport properties.