Complementary etching behavior of alkali, metal‐catalyzed chemical, and post‐etching of multicrystalline silicon wafers

Both alkali and metal‐catalyzed chemical etching (MCCE) of multicrystalline silicon (mc‐Si) wafer show anisotropic etching behavior, resulting in different morphologies among the different grains. However, by combining alkali etching, MCCE, and a post‐etching process, homogeneous microstructures can be obtained on the surface of mc‐Si wafer. After the first alkali etching, there are three typical morphologies of upward pyramids, terraces, and tilt planes, and relative to the initial Si(100), Si(110), and Si(111) dominated grains, these show low, moderate, and high reflection, respectively. After MCCE and the post‐etching process, the microstructures on the different grains have converged to a similar morphology and reflection. Mc‐Si solar cells fabricated by complementary alkali etching, MCCE, and post‐etching have a good appearance and high efficiency of ~19.4%. Moreover, the cells with submicrometer texture have the advantages of reverse current‐voltage characteristics and weak light response over traditional cells with micrometer texture. We succeeded in obtaining the homogeneous microstructures and the less color difference among grains on the surface of mc‐Si wafer by anisotropic alkali etching, MCCE, and post‐etching, which show complementary etching behavior on certain grains. The mc‐Si solar cells made from the complementary etching behavior show good appearance and high efficiency ~19.4%, and have higher reverse breakdown voltages and better weak light performances than that of H‐DRE cells.