Abstract
The so called inverted pyramid arrays, outperforming conventional upright pyramid textures, have been successfully achieved by one-step Cu assisted chemical etching (CACE) for light reflection minimization in silicon solar cells. Due to the lower reduction potential of Cu2+/Cu and different electronic properties of different Si planes, the etching of Si substrate shows orientation-dependent. Different from the upright pyramid obtained by alkaline solutions, the formation of inverted pyramid results from the coexistence of anisotropic etching and localized etching process. The obtained structure is bounded by Si {111} planes which have the lowest etching rate, no matter what orientation of Si substrate is. The Si etching rate and (100)/(111) etching ratio are quantitatively analyzed. The different behaviors of anisotropic etching of Si by alkaline and Cu based acid etchant have been systematically investigated.
Highlights
Silicon (Si) surface texturing is an indispensable step for the fabrication of Si solar cells due to the high reflection of planar Si wafers
Wang et al discovered a new technical solution to fabricate micrometer sized inverted pyramidal structure by maskless Cu-nanoparticles assisted chemical etching in Cu(NO3)2/HF/H2O2/H2O solutions[14,15,16], which had lower reflectivity and higher light absorption, along with a shorter etching time and a lower etching temperature during the texturing process compared with the industrial pyramidal structure texturization
More detailed analysis will be proposed for the anisotropic etching of Si based on a HF/H2O2 process with the assistance of Cu nanoparticles by taking advantage of the anisotropic electrochemical behavior of a Si crystal
Summary
Silicon (Si) surface texturing is an indispensable step for the fabrication of Si solar cells due to the high reflection of planar Si wafers. Wang et al discovered a new technical solution to fabricate micrometer sized inverted pyramidal structure by maskless Cu-nanoparticles assisted chemical etching in Cu(NO3)2/HF/H2O2/H2O solutions[14,15,16], which had lower reflectivity and higher light absorption, along with a shorter etching time and a lower etching temperature during the texturing process compared with the industrial pyramidal structure texturization. Both upright pyramids and inverted pyramids are the consequence of anisotropic etching of Si (100) substrate, which are bounded by {111} crystallographic planes due to the slowest etching rate of {111} planes.
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