Bär, M.; Schubert, B.-A.; Marsen, B.; Krause, S.; Pookpanratana, S.; Unold, T.; Weinhardt, L.; Heske, C.; Schock, H.-W.: Impact of KCN etching on the chemical and electronic surface structure of Cu2ZnSnS4 thin-film solar cell absorbers. Applied Physics Letters 99 (2011), p. 152111/1-4
10.1063/1.3650717
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 is found to significantly alter the surface composition and can best be explained by a preferred etching of Cu and, to a lesser degree, Sn. As a result, we also find a significant increase of the surface band gap; for a Cu-poor processed sample, the band gap increases from (1.53±0.15) eV, in good agreement with optically derived bulk band gap values, to (1.91±0.15) eV.