Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 26: Poster Session
MM 26.63: Poster
Tuesday, March 23, 2010, 14:45–16:30, Poster C
Electrical properties of grain boundaries in Cu(In,Ga)(S,Se)2 thin films for solar cells — •Jaison Kavalakkatt, Daniel Abou-Ras, Melanie Nichterwitz, Raquel Caballero, Björn Marsen, Thorsten Rissom, Thomas Unold, and Hans-Werner Schock — Helmholtz Center Berlin for Materials and Energy, Berlin, Germany
Electron-beam-induced current (EBIC) and electron backscatter diffraction (EBSD) in a scanning electron microscope are powerful tools to investigate the electrical and microstructural properties of grains and grain boundaries in Cu(In,Ga)(S,Se)2 absorber layers in thin-film solar cells. For the present investigation, the Mo/glass stack was stripped off the remaining Cu(In,Ga)(S,Se)2/CdS/ZnO heterojunction, in order to prepare a Cu(In,Ga)(S,Se)2 surface with reduced roughness, leading to both, high-quality EBSD patterns and decreased number of topography artefacts in EBIC distribution images. In comparison to EBIC analyses on cross-section samples, the measurements on back-surfaces increase the number of accessible grain boundaries and therefore improve the statistics of their electrical properties. EBSD maps identify clearly the positions of the grain boundaries as well as allow for their classifications. Across various grain boundaries, profiles were extracted from EBIC distribution images. Corresponding simulation of these profiles provide values for minority-carrier diffusion lengths and recombination velocities at grain boundaries. The general result for Cu(In,Ga)Se2 layers with various In/Ga ratios as well as Cu concentrations is a similar collection at grain interiors and Σ3 grain boundaries and a reduced charge-carrier collection at non-Σ3 grain boundaries.