研究目的
To determine the band alignment at the CdTe/SnTe heterojunction interface for CdTe thin-film solar cells and to verify the feasibility of using SnTe as a back contact buffer layer.
研究成果
The band alignment at the CdTe/SnTe interface is an ideal type-I band structure for CdTe solar cells, with VBO of 1.33 ± 0.18 eV and CBO of 0.09 ± 0.18 eV. The feasibility of using SnTe as a solar cell back contact is confirmed.
研究不足
The measured band alignment data obtained by XPS measurements could be affected by several factors such as strain and band bending effect.
1：Experimental Design and Method Selection:
The valence band offsets in MBE-grown cadmium telluride (CdTe)/tin telluride (SnTe) (111) heterostructures were measured with X-ray photoelectron spectroscopy (XPS).
2：Sample Selection and Data Sources:
SnTe, CdTe, and CdTe/SnTe (111) HJs were grown on freshly cleaved BaF2 (111) substrates.
3：List of Experimental Equipment and Materials:
Integrated ultrahigh vacuum system equipped with multifunction surface analysis system (Kratos Axis Supra XPS), telluride MBE system, BaF2 substrates.
4：Experimental Procedures and Operational Workflow:
The substrates were prebaked for 15 min at 500 ?C before the growth. SnTe and PbTe films of about
5：5 μm thickness were grown at a rate of 1 μm/h and substrate temperature of T = 265 ?C and T = 250 ?C, respectively. The CdTe/SnTe sample was grown under the same parameters and the CdTe layer was estimated to have a thickness of ～10 nm from growth rate calibrations. In situ reflection high-energy electron diffraction (RHEED) was used to monitor growth process. Data Analysis Methods:
The VBO of the CdTe/SnTe interface was calculated using a widely used method proposed by Kraut et al.
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