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HL: Halbleiterphysik

HL 32: Photovoltaic

HL 32.14: Vortrag

Mittwoch, 29. März 2006, 18:00–18:15, BEY 118

Symmetry of defects in chalcopyrites - a polarized photoluminescence study — •Sven Augustin, Susanne Siebentritt, and Martha Lux-Steiner — Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin

Defects in the chalcopyrite CuGaSe_2 are analysed. CuGaSe_2 is used as an absorber in thin-film solar cells. As is known for a p-n junction, an important contribution to the efficiency is made by choosing the concentration of defects. So one way to improve efficiency is to find the optimal fraction of defects in the material. The first step in achieving this goal for CuGaSe_2 is to determine the nature of the dopants, i.e. the chemical and the structural (lattice site) character. By pursuing this aim the method of polarization resolved photo luminescence (PL) and PL excitation (PLE) spectroscopy is used to obtain information on the symmetry of the defects. The measurements of epitaxial samples of different orientation show, that the emission from two of the acceptors is polarized mainly parallel to the c-axis of the tetragonal crystal and the third acceptor on the other hand radiates with polarization predominantly perpendicular to the c-axis. Employing a classical oszillator model allows to ascertain the symmetry of the defects.