Dresden 2014 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 112: Energy materials: CIGS and related photovoltaics
HL 112.5: Vortrag
Freitag, 4. April 2014, 10:30–10:45, POT 112
Impact of Gallium on chemical gradients in Cu(In,Ga)Se2 thin film solar cells grown on flexible polyimide substrate — •Stefan Ribbe1,2, Andreas Rahm1, Frank Bertram2, and Jürgen Christen2 — 1Solarion AG, Ostende 5, 04288 Leipzig, Germany — 2Institute for Experimental Physics, Otto-von-Guericke-Universität Magdeburg, Germany
Cu(In,Ga)Se2(CIGS) thin film solar cells on polyimide substrate receive a high interest for many applications due to its flexibility and weight-lightness. Lower growth temperatures - a requirement of using polyimide substrate - are a challenge for producing high efficiency CIGS material. In particular the proper adjustment of the vertical gallium gradient directly affects amongst other properties the collection of photogenerated carriers.
CIGS layers were grown on flexible polyimide foil by using an ion-beam assisted roll-to-roll process. Sodium was provided by an additional source of NaF during the three-stage process to ensure high conversion efficiency. Gallium content was varied by the growth rate controlled by XRF (x-ray fluorenscence).
Lateral microscopical fluctuations of the GGI (Ga/(Ga+In)-ratio) and changes of the vertical gallium gradient within the CIGS absorber layers have been studied by highly spatially resolved cathodoluminescence microscopy (CL) at low temperature (T = 5K). Spectral Linescans on cross sections directly show a change of a smooth vertical gradient to a discontinuous shift of the peak wavelength in dependence of the gallium content in the CIGS layers