Recrystallization of Cu(In,Ga)Se2 thin films studied by X-ray diffraction

A recrystallization is essential for the synthesis of highest quality Cu(In,Ga)Se2 (CIGSe) thin films for solar cell applications. Here we present a real-time study of the recrystallization of CIGSe thin films. We trigger the recrystallization by allowing diffusion of Cu into a Cu-poor CIGSe film and use synchrotron-based energy-dispersive X-ray diffraction to monitor this transition in real time. Additionally, we characterize the films by means of angledispersive X-ray diffraction. Before recrystallization, the Xray diffraction patterns exhibit a diffraction maximum that does not correspond to the ideal chalcopyrite structure of CIGSe. We attribute this maximum to stacking faults within the bulk of the films by modeling diffraction patterns of faulted CIGSe with the software DIFFaX. This diffraction maximum is detected at temperatures below 650 K and is absent at temperatures above 750 K, indicating that the faults in question were annihilated in this temperature range. This process occurs after the incorporation of Cu into the Cu-poor CIGSe lattice which takes place in the 550K to 650K temperature range.  2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Doi: 10.1016/j.actamat.2013.04.006