研究目的
Investigating the impact of different front contact topography types on the optical effects of light-coupling and light-trapping in solar cells, specifically in a-Si:H/μc-Si:H tandem solar cells.
研究成果
The study demonstrated that the two optical effects of light-coupling and light-trapping are caused by different texture features. A double texture was needed to generate a suitable texture for maximum current output, combining large features with significant depth for good light-trapping and smaller very sharp features for good light-coupling. An optimized double-textured ZnO:Al yielded 12.5% initial efficiency in an a-Si:H/μc-Si:H solar cell with only a 1.64 μm total absorber layer thickness.
研究不足
The study acknowledges that the spread in electrical properties and slightly different film thicknesses might cause minor effects of parasitic free carrier absorption in the long wavelength range. Additionally, the crystallinity of the μc-Si:H bottom cell was affected by different front contact textures, which could lead to variations in absorption coefficients.
1：Experimental Design and Method Selection:
The study utilized sputter-deposited aluminum-doped zinc oxide (ZnO:Al) and subsequent wet-chemical etching to demonstrate various kinds of textures that exhibit different abilities for light-trapping and light-coupling. As a detector, a silicon thin-film tandem solar cell consisting of hydrogenated amorphous and microcrystalline silicon as absorber was applied.
2：Sample Selection and Data Sources:
The samples were prepared on
3：3 mm thick float glass with a size of 10 × 10 cm2, upon which a 120 nm SiOxNy thin-film was deposited via reactive sputter deposition. List of Experimental Equipment and Materials:
The ZnO:Al films were deposited in a vertical inline sputter deposition system (VISS 300) by von Ardenne Anlagentechnik, Dresden, Germany. The texturing step was performed either in
4：5 w/w% HCl, or 1 w/w% HF, or a combination of double etching processes. Experimental Procedures and Operational Workflow:
After etching, the sample surfaces were characterized by atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements. The light-scattering properties of the rough ZnO:Al and silicon/back contact interfaces were analyzed using angular resolved scattering (ARS) measurements of the reflected light.
5：Data Analysis Methods:
The 3D topography data from AFM measurements were analyzed using a watershed algorithm to detect the surface features' boundaries and statistically evaluate the average feature diameter.
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