Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 31: Organic semiconductors
HL 31.9: Vortrag
Mittwoch, 29. März 2006, 16:45–17:00, POT 51
Efficient photosensitization of C60 microcrystals with II-VI and III-V semiconductor nanocrystals — •A. Biebersdorf1, R. Dietmüller1, A. S. Susha1, A. L. Rogach1, S. K. Poznyak2, D. V. Talapin3, H. Weller3, T. A. Klar1, and J. Feldmann1 — 1Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universität, München — 2Physico-Chemical Research Institute, Belarusian State University, 220050 Minsk, Belarus — 3Institute of Physical Chemistry, University of Hamburg
Photoconductors are essential and common components of optoelectronic devices such as photodetectors or photocopying machines. The sensitivity and spectral range of photoconductors can be drastically improved by sensitizers, which absorb light and provide additional charge carriers to the photoconducting material.
In the present report we demonstrate that semiconductor nanocrystals (NCs) such as CdSe, CdTe and InP can efficiently photosensitize needle-like C60 microcrystals. A significant increase in photocurrent (by 3 orders of magnitude) is observed for C60 microcrystals covered with NCs, in comparison with C60 microcrystals without NCs. The photocurrent spectrum of C60 / NCs composites is close to the NC absorption spectrum and can be tuned precisely by the NC size. Maximum external quantum efficiency was estimated by calculating the number of photoelectrons per incident photon and is about 10 % for the CdSe / C60 composites and about 3 % for InP / C60 composites.
We explain the increased photoconductivity in the following way: The photoexcited electrons in the NCs are transferred to the C60 microcrystals causing photoconductivity, while the holes remain trapped in the NCs.