TY - GEN A1 - Bär, Marcus A1 - Schubert, Björn-Arvid A1 - Marsen, Björn A1 - Krause, Stefan A1 - Pookpanratana, Sujitra A1 - Unold, Thomas A1 - Weinhardt, Lothar A1 - Heske, Clemens A1 - Schock, Hans-Werner T1 - Impact of KCN etching on the chemical and electronic surface structure of Cu2ZnSnS4 thin-film solar cell absorbers N2 - The chemical and electronic surface structure of Cu2ZnSnS4 thin-film solar cell absorbers has been investigated by direct and inverse photoemission. Particular emphasis was placed on the impact of KCN etching, which significantly alters the surface composition and is best explained by a preferred etching of Cu and, to a lesser degree, Sn. As a consequence the surface band gap increased from (1.53 +/- 0.15) eV, which agrees with optically derived bulk band gap values, to (1.91 +/- 0.15) ev. KW - kesterite KW - thin-film solar cells KW - electronic surface structure Y1 - 2011 ER - TY - GEN A1 - Sullivan, J. T. A1 - Wilks, Regan G. A1 - Winkler, M. T. A1 - Weinhardt, Lothar A1 - Recht, D. A1 - Said, A. J. A1 - Newman, B. K. A1 - Zhang, Y. A1 - Blum, Monika A1 - Krause, S. A1 - Yang, Wan Li A1 - Heske, Clemens A1 - Aziz, M. J. A1 - Bär, Marcus A1 - Buonassisi, T. T1 - Soft x-ray emission spectroscopy studies of the electronic structure of silicon supersaturated with sulfur N2 - We apply soft x-ray emission spectroscopy (XES) to measure the electronic structure of crystalline silicon supersaturated with sulfur (up to 0.7 at. %), a candidate intermediate-band solar cell material. Si L2,3 emission features are observed above the conventional Si valence band maximum, with intensity scaling linearly with S concentration. The lineshape of the S-induced features change across the insulator-to-metal transition, indicating a significant modification of the local electronic structure concurrent with the change in macroscopic electronic behavior. The relationship between the Si L2,3 XES spectral features and the anomalously high sub-band gap infrared absorption is discussed. KW - black silicon KW - solar cells KW - electronic surface structure KW - x-ray emission spectroscopy Y1 - 2011 ER -