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Selective Removal of ZnSe in Zn-Rich Cu2ZnSnSe4 Films: a New Oxidizing Approach
S. López-Marino, Y. Sánchez, M. Placidi, A. Fairbrother, M. Espindola-Rodriguez, X. Fontané, V. Izquierdo-Roca, J. Lopez-Garcia, L. Calvo-Barrio, A. Pérez-Rodríguez, E. Saucedo
Subtopic: CdTe, CIS and Related Ternary and Quaternary Thin Film Solar Cells
Event: 28th European Photovoltaic Solar Energy Conference and Exhibition
Session: 3BV.6.57
ISBN: 3-936338-33-7
0,00 EUR
Document(s): poster


An innovative route for the selective removal of ZnSe on Zn-rich and Cu-poor Cu2ZnSnSe4 films is presented, based on the use of a mixture of an oxidizing agent and a mineral acid. We have tested three oxidizing agents: H2O2, KMnO4 and K2Cr2O7, combined with different concentrations of H2SO4. With all of these agents Se-2 is always selectively oxidized to Se0 from the ZnSe phase, while the CZTSe layer remains almost unaffected. This leads to the formation of an elemental selenium capping layer onto the absorber, which is subsequently removed with a Na2S solution. By using pure H2O2, we observe a complete oxidation of Se-2 to Se+6, avoiding the formation of solid Se0 during the process, but with some evidence of CZTSe deterioration. In contrast, by using the oxidizing approach in a H2SO4–based medium, we observe a large improvement on the conversion efficiency of the devices after removal of elemental Se. This is mainly related to an improvement on the FF and Voc, resulting from the ZnSe selective etch.