A new technique of surface passivation of silicon substrates by quinhydrone/ethanol treatment has been investigated. To estimate the surface passivation effect, the lifetimes of the silicon substrates were measured using the microwave photoconductive decay method. The measured lifetimes were dependent on quinhydrone concentration and passivation time. The 0.01 mol/dm3 quinhydrone/ethanol treatment showed a good passivation effect, and a very low surface recombination velocity was obtained. The quinhydrone/ethanol treatment was a more effective passivation technique than the iodine/ethanol treatment. Therefore, the quinhydrone/ethanol passivation can be widely used for lifetime measurement.
We present device performance of solar cells based on multicrystalline SiGe (mc-SiGe) bulk crystal with microscopic compositional distribution grown by the casting method. The average Ge composition was systematically changed in the range between 0% and 10%. A small addition of Ge to multicrystalline Si (mc-Si) was found to be very effective to increase the short-circuit current density without affecting the open-circuit voltage. As a consequence, the overall efficiency of a solar cell based on mc-SiGe was improved compared with that based on mc-Si. This result demonstrates that mc-SiGe is a promising candidate to replace mc-Si since it could achieve higher conversion efficiency without drastic increase of the production cost.
The effect of optical confinement in textured antireflection coating (AR coating) was investigated. Textured ZnO films prepared by metalorganic chemical vapor deposition were applied to solar cells as AR coating. The reflectance of the cells decreased as the grain size increased with film thickness, especially at long wavelength. This reduction in the reflectance caused an increase in short-circuit current and spectral response of the cells at near-infrared. The effect of optical confinement in the cell by this film was shown as far as long-wavelength range was concerned.
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