Growth And Properties Of Emerging Photovoltaic Materials Chalcogenide Perovskite Thin Films

The growth of mankind’s demand for energy will inevitably put forward higher requirements for the utilization of solar energy.Chalcogenide perovskite is a promising candidate material for solar cells,with its excellent photoelectric conversion efficiency,suitable bandgap width,non-toxic element composition,and stable structure.It,thus,has attracted extensive attention of researchers.Thus far,most of the investigations are focused on the chalcogenide perovskite powder.The preparation of high-quality epitaxial thin films at the nanoscale is a prerequisite for further exploration of the physical properties of the material.In this paper,based on pulsed laser deposition technology and thin film characterization technology,the typical chalcogenide perovskite BaZrS₃ is used as the material to investigate the epitaxial growth mechanism and associated physical properties of thin films made from chalcogenide perovskite.The main research contents are as follows:（1）The BaZrS₃ single crystal epitaxial thin film was successfully prepared on yttrium-doped zirconia（YSZ）substrate by pulsed laser deposition（PLD）technique,and the"growth window"for preparing BaZrS₃ single crystal epitaxial thin film on YSZ substrate was explored.Through structural characterization of BaZrS₃ single crystal epitaxial film via XRD,XPS and TEM techniques,it is found that the BaZrS₃ single crystal epitaxial film prepared in this study has a good epitaxial relationship with the substrate.The AFM characterization results show that the surface of the film is relatively smooth and flat,and the RMS can be optimized to within 2.217 nm.（2）The optical properties of BaZrS₃ single crystal epitaxial thin film were tested.The results of Raman spectroscopy test show that the thin films prepared show B_1g¹,A_g⁴,B_2g⁶,B_3g⁵ vibration models,which are consistent with those reported in reference.UV-Vis test results show that the thin film products heat-treated at 800°C for 5 hours have the best optical absorption,and the absorption coefficient of BaZrS₃ thin film samples rises rapidly in the energy range of 1.7 eV-1.8 eV under these conditions.The value is 1.1×10⁵ cm^-1,and the optical band spacing is 1.75 eV.At the same time,the test results of Photoluminescence also show that the sample has a clear PL peak at 1.74 eV.（3）The verification test of ferroelectricity was carried out on the high-quality BaZrS3 single crystal epitaxial film.In this paper,the BaZrS₃/TiN/YSZ system is designed as the thin film sample for PFM characterization.In the prepared thin film sample a phenomenon of local polarization reversal is observed,which is the most obvious under the condition of heat treatment at 800℃for 5 h.Its amplitude curve and phase curve were found to conform to the law of the ferroelectric material curve.This result provides strong evidence for the ferroelectricity of the BaZrS₃ single crystal epitaxial film prepared on the YSZ substrate.