研究目的
Developing a viable metrology technique for thickness measurement of multilayer film stacks in perovskite solar cells using spectroscopic ellipsometry.
研究成果
The study developed a consistent procedure for building a working SE model for bilayer and/or trilayer heterojunction material stacks that consist of multiple transparent layers. This methodology should also be applicable for other hole and electron transport materials applied to organic lead halide perovskite solar cells. Once established, these models should allow for fast and repeatable ellipsometry characterization of these photovoltaic devices, including the thicknesses and optical properties of constituent layers.
研究不足
The study faced challenges such as roughness at each heterointerface, similarities in optical spectra of transparent layers, and anomalous dispersion of perovskite. The introduction of a BEMA layer compromised the MSE as well as measured thicknesses due to the increased number of variables for the additional layer(s).
1:Experimental Design and Method Selection:
The study utilized spectroscopic ellipsometry (SE) for thickness measurement and optical property analysis of perovskite solar cell layers. The J. A. Wollam M2000 ellipsometer was used for collecting SE spectra, and CompleteEASE software was used for analysis and modeling.
2:Sample Selection and Data Sources:
Individual thin films and thin film stacks were deposited on glass substrates or ITO/glass substrates. The thickness of the films was varied either by changing the spin speed or the solution concentration.
3:List of Experimental Equipment and Materials:
Equipment included the J. A. Wollam M2000 ellipsometer, Bruker DektakXT profilometer, FEI Helios NanoLab 400 DualBeam field emission scanning electron microscope, Bruker Dimension ICON atomic force microscope, and Rigaku SmartLab diffractometer.
4:Experimental Procedures and Operational Workflow:
The process involved building an ellipsometry model from scratch for thickness measurement of MAPI perovskite and ITO/HTL bilayer thin film stacks on a glass substrate. Three HTLs (CuI, Cu2O, and PEDOT:PSS) were studied.
5:Data Analysis Methods:
Optical constants of all the representative thin films were extracted for a wide wavelength range (300 nm–900 nm). The models were validated using profilometry, AFM, and SEM measurements.
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