| AVS 64th International Symposium & Exhibition | |
| Spectroscopic Ellipsometry Focus Topic | Monday Sessions |
| Session EL+AS+EM+TF-MoM |
| Session: | Application of SE for the Characterization of Thin Films and Nanostructures |
| Presenter: | Honggang Gu, Huazhong University of Science and Technology, China |
| Authors: | H.G. Gu, Huazhong University of Science and Technology, China S.R. Li, Huazhong University of Science and Technology, China B.K. Song, Huazhong University of Science and Technology, China J. Tang, Huazhong University of Science and Technology, China S.Y. Liu, Huazhong University of Science and Technology, China |
| Correspondent: | Click to Email |
During the past several years, the organic-inorganic lead halide perovskites (APbX3, A = CH3NH3 or NH2CHNH2, X = Cl, Br, or I) have been promising materials for photovoltaic, photoelectric -detecting and light-emitting devices due to their outstanding photoelectric properties, such as broad absorption range, high quantum efficiency, ultrafast charge generation, high charge carrier mobility and long charge carrier lifetime and diffusion length. However, there are two remaining challenges that need to be addressed in order to apply these materials to photoelectric productions, namely the compound stability and the presence of lead. Most recently, lead-free metal halide double perovskites, such as Cs2AgBiCl6 and Cs2AgInCl6, have attracted extensive attention because of their nontoxicity and relative air-stability. In the study and application of these perovskite materials, the knowledge of their optical properties, such as the bandgap and the basic optical constants, is of great importance to predict the photoelectric characteristics and dig the potential of the materials.
Spectroscopic ellipsometry (SE) has been developed as a powerful tool to characterize the optical properties as well as structure parameters of novel materials, thin films and nanostructures. In this work, we study the optical properties of Cs2AgIn(1-x)BixCl6 perovskites by a spectroscopic ellipsometer (ME-L ellipsometer, Wuhan Eoptics Technology Co., Wuhan, China). The refractive index and the extinction coefficient of Cs2AgIn(1-x)BixCl6 with different composition coefficient x of bismuth are determined by the ellipsometer over the wavelength range of 250-1000nm. We find that the presence of bismuth introduces two critical points in the optical constant spectra of the perovskites, i.e., 315nm and 382nm in the refractive index spectra and 300nm and 375nm in the extinction coefficient spectra, respectively. Moreover, there is a red shift in the bandgaps and significant increase in both the refractive index and the extinction coefficient with the increase of composition coefficient x of bismuth.