@misc{BaerSchubertMarsenetal., author = {B{\"a}r, Marcus and Schubert, Bj{\"o}rn-Arvid and Marsen, Bj{\"o}rn and Wilks, Regan G. and Pookpanratana, Sujitra and Blum, Monika and Krause, Stefan and Unold, Thomas and Yang, Wan Li and Weinhardt, Lothar and Heske, Clemens and Schock, Hans-Werner}, title = {Cliff-like conduction band offset and KCN-induced recombination barrier enhancement at the CdS/Cu2ZnSnS4 thin-film solar cell heterojunction}, abstract = {The electronic structure of the CdS/Cu2ZnSnS4 (CZTS) heterojunction was investigated by direct and inverse photoemission. The effects of a KCN etch of the CZTS absorber prior to CdS deposition on the band alignment at the respective interface were studied. We find a "cliff"-like conduction band offset at the CdS/CZTS interface independent of absorber pretreatment and a significant etch-induced enhancement of the energetic barrier for charge carrier recombination across the CdS/CZTS interface.}, language = {en} } @misc{BaerSchubertMarsenetal., author = {B{\"a}r, Marcus and Schubert, Bj{\"o}rn-Arvid and Marsen, Bj{\"o}rn and Krause, Stefan and Pookpanratana, Sujitra and Unold, Thomas and Weinhardt, Lothar and Heske, Clemens and Schock, Hans-Werner}, title = {Impact of KCN etching on the chemical and electronic surface structure of Cu2ZnSnS4 thin-film solar cell absorbers}, abstract = {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.}, language = {en} } @misc{BaerSchubertMarsenetal., author = {B{\"a}r, Marcus and Schubert, Bj{\"o}rn-Arvid and Marsen, Bj{\"o}rn and Wilks, Regan G. and Blum, M. and Krause, S. and Pookpanratana, Sujitra and Zhang, Y. and Unold, Thomas and Yang, W. and Weinhardt, Lothar and Heske, Clemens and Schock, Hans-Werner}, title = {Cu2ZnSnS4 thin-film solar cell absorbers illuminated by soft x-rays}, series = {Journal of Materials Research}, volume = {27}, journal = {Journal of Materials Research}, number = {8}, issn = {2044-5326}, doi = {10.1557/jmr.2012.59}, pages = {1097 -- 1104}, abstract = {In view of the complexity of thin-film solar cells, which are comprised of a multitude of layers, interfaces, surfaces, elements, impurities, etc., it is crucial to characterize and understand the chemical and electronic structure of these components. Because of the high complexity of the Cu2ZnSn(S,Se)4 compound semiconductor absorber material alone, this is particularly true for kesterite-based devices. Hence, this paper reviews our recent progress in the characterization of Cu2ZnSnS4 (CZTS) thin films. It is demonstrated that a combination of different soft x-ray spectroscopies is an extraordinarily powerful method for illuminating the chemical and electronic material characteristics from many different perspectives, ultimately resulting in a comprehensive picture of these properties. The focus of the article will be on secondary impurity phases, electronic structure, native oxidation, and the CZTS surface composition.}, language = {en} } @misc{BlumOdeliusWeinhardtetal., author = {Blum, M. and Odelius, Michael and Weinhardt, Lothar and Pookpanratana, Sujitra and B{\"a}r, Marcus and Zhang, Y. and Fuchs, Oliver and Yang, W. and Umbach, Eberhard and Heske, Clemens}, title = {Ultrafast Proton Dynamics in Aqueous Amino Acid Solutions Studied by Resonant Inelastic Soft X‑ray Scattering}, series = {The Journal of physical chemistry : B}, volume = {116}, journal = {The Journal of physical chemistry : B}, number = {46}, issn = {1520-5207}, pages = {13757 -- 13764}, abstract = {Resonant inelastic soft X-ray scattering (RIXS) has been used to study the electronic structure of glycine and lysine in aqueous solution. Upon variation of the pH value of the solution from acidic to basic, major changes of the nitrogen K edge RIXS data are observed for both amino acids, which are associated with the protonation and deprotonation of the amino groups. The experimental results are compared with simulations based on density functional theory, yielding a detailed understanding of the spectral changes, as well as insights into the ultrafast proton dynamics in the intermediate core-excited/ionized state of the RIXS process.}, language = {en} } @misc{BaerCouzinieDevyDuarteetal., author = {B{\"a}r, Marcus and Couzini{\`e}-Devy, Fran{\c{c}}ois and Duarte, Roberto Felix and Klaer, Joachim and Pookpanratana, Sujitra and Blum, Monika and Zhang, Yi and Denlinger, Jonathan D. and Yang, Wanli and Wilks, Regan G. and Weinhardt, Lothar and Schock, Hans-Werner and Southerland Kessler, Jude and Heske, Clemens}, title = {The Heavily Intermixed In2S3/Cu(In,Ga)Se2 Interface as Revealed by Photoelectron and Soft X-ray Emission Spectroscopy}, series = {2013 IEEE 39th Photovoltaic Specialists Conference, (PVSC 2013), Tampa, Florida, USA, 16 - 21 June 2013}, journal = {2013 IEEE 39th Photovoltaic Specialists Conference, (PVSC 2013), Tampa, Florida, USA, 16 - 21 June 2013}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-4799-3300-6}, doi = {10.1109/PVSC.2013.6744280}, pages = {857 -- 862}, language = {en} } @misc{WeinhardtFuchsFischeretal., author = {Weinhardt, Lothar and Fuchs, Oliver and Fischer, Andr{\´e} and Weigand, Markus and Meyer, Frank and Benkert, Andreas and Blum, Monika and B{\"a}r, Marcus and Pookpanratana, Sujitra and Denlinger, Jonathan D. and Heske, Clemens and Umbach, Eberhard}, title = {Site- and Symmetry-resolved Resonant X-ray Emission Study of a Highly-ordered PTCDA Thin Film}, series = {The Journal of Physical Chemistry: C}, volume = {120}, journal = {The Journal of Physical Chemistry: C}, number = {16}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.5b12422}, pages = {8607 -- 8615}, language = {en} }