Determination and interpretation of the optical constants for solar cell materials

• Published in: Applied surface science 2017-11, Vol.421, p.276-282
• Main Authors: Fujiwara, Hiroyuki, Fujimoto, Shohei, Tamakoshi, Masato, Kato, Masato, Kadowaki, Hideyuki, Miyadera, Tetsuhiko, Tampo, Hitoshi, Chikamatsu, Masayuki, Shibata, Hajime
• Format: Article
• Language: English
• Subjects: Absorption coefficient; Density functional theory; Solar cell materials; Spectroscopic ellipsometry; Surface roughness
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.09.113

[Display omitted] •Effect of very rough surface on spectroscopic ellipsometry analysis is determined.•A simple procedure for the correction of underestimated roughness is established.•The optical transitions in CH3NH3PbI3 and Cu2ZnSnSe4 are analyzed by DFT. Solar cell materials in thin film form often exhibit quite rough surface, which makes the accurate determination of the optical constants using spectroscopic ellipsometry (SE) quite difficult. In this study, we investigate the effect of the rough surface on the SE analysis and establish an analysis procedure, which is quite helpful for the correction of the underestimated roughness contribution. As examples, the roughness analyses for CuInSe2 and CH3NH3PbI3 hybrid-perovskite thin films are presented. Moreover, to interpret the dielectric functions of emerging solar cell materials, such as CH3NH3PbI3 and Cu2ZnSnSe4, the optical transition analyses are performed based on density functional theory (DFT). The excellent agreement observed between the experimental and DFT results allows the detailed assignment of the transition peaks, confirming the importance of DFT for revealing fundamental optical characteristics.