OPTIMIZATION OF POROUS SILICON CHARACTERISTICS FOR SOLAR BATTERIES

Abstract

The aim is to form the anti-reflective layers of porous silicon on the solar cell surface in the presence of the current-collecting contact comb at the effective area, as well as the study of the state of front contact system of solar cells after etching on their main characteristics.The analysis of the influence of electrochemical etching on the state of the solar cell front contact system without antireflection coating was carried out on the basis of the dependences of the reflectance spectrum of porous silicon on its thickness and refractive index. In the range of wavelengths of 550-850 nm, a minimal reflection from the porous layer surface for the thickness of porous silicon from 70 to 100 nm was found, and its refractive index ranges from 1.35 to 1.9.The critical time of staying of the solar cell structure in the electrolyte, the excess of which leads to the damage of contact fingers of the front current-collecting contact comb was found. For anodization in an electrolyte C2 H5 OH:HF=1:1, the critical time was 45 s. The reduction of the anodizing time to 10 s at anodic charge density of 0.46 C/cm2 allowed to obtain porous silicon layers without significant damage to the current-collecting comb. By reducing the duration of electrochemical treatment to 3-6 s and increasing the anode current, it was possible to completely prevent the damage of the contact system.The results of study of the main solar cell parameters before and after formation of anti-reflective layer on the basis of porous silicon showed that for mono- and multicrystalline solar cells the increase in photocurrent exceeded 50%, the efficiency increased by 25% and 22% respectively for mono- and multicrystalline samples. At the same time, for all tested samples, the open-circuit voltage decreased by 2.5%, and the fill factor degraded by 10.7% and 18.8% for mono- and multicrystalline solar cells, respectively.