Control of two-step growth processes of chalcopyrite thin ®lms by X-ray ¯uorescence spectroscopy

Thin ®lm photovoltaic devices based on chalcopyrite absorber layers are important candidates for the large-scale production of economically viable solar cells and modules. The material quality of the polycrystalline absorber layers is critically in¯uenced by the bulk compositional uniformity of these ®lms. In this regard, it has been generally reported that the structural and electronic properties of two-step processed chalcopyrite thin ®lms are dominated by metal losses during the high temperature selenization steps. In this study, precursor ®lms of copper and indium and/or gallium were selenized by different techniques at varying temperatures. The samples were analyzed by X-ray ¯uorescence (XRF) before and after each reaction step. The generally reported loss of indium and/or gallium during selenization at elevated temperatures was contradicted by XRF measurements (i.e. the amount of the metals remained constant at typical process temperatures). The apparent material losses are explained in terms of a measurement artifact of the widely used electron probe microanalysis (EPMA or EDX) due to metal segregation. # 2001 Elsevier Science B.V. All rights reserved