Application of Anti-reflection coating for silicon solar cell

Abstract

High efficiency solar cells should have a low reflection for the incident light beam. Optical losses in solar cells originate from three major sources: surface reflection, top grid shadowing, and inadequate absorption by either excess energy photons or weak energy photons. In an attempt to reduce the surface reflectance for silicon (Si) surfaces, they are coated by single, double layer or multilayer, anti-reflection films, which could reduce the surface reflectance to about 2 %. Antireflection coatings (ARCs) became one of the key issues for mass production of Si solar cells. They are generally examined by a computer system before being performed on the solar cell surface to ensure enhancement of the solar energy transmitted to the cells and thus increasing its efficiencies. Antireflection coatings on high index substrate are theoretically investigated. Also, the short circuit current, open circuit voltage, maximum current density, maximum voltage, maximum power and energy conversion efficiency of the cell are determined. To cover the effect of the surface modifications on the cell output parameters a study on the external quantum efficiency is introduced. To overcome surface problems, this study introduces two approaches: single and double layer anti-reflection coating (ARC) designs taking into consideration the group propagation of waves. Material dispersions are considered all over the present study.

Four designs are presented to compare the cell performance before and after coating. Design I consists of Si solar cell as a substrate and one layer dielectric thin film. The layer details are as follows; mono oxide silicon SiO film with refractive index 1.875 at 700nm and thickness equal to 93.312 nm corresponding to quarter of 700nm as monitoring wavelength. Design ΙΙ consists of Si solar cell as a substrate and double dielectric layers deposited on it at single monitoring wavelength λo equals 700 nm. The layers are: 〖MgF〗_2 as air interface material with refractive index at the monitoring equals 1.378 and TiO_2 as a substrate interface material with refractive index at λo equals 2.263. The thicknesses for these two layers are 126.981nm and 69.115nm respectivlly. Design ΙΙI is the first solution of the Catalan analysis consists of Si solar cell as a substrate and double dielectric layers deposited on it at single monitoring wavelength equals 700 nm. The layers are: 〖MgF〗_2 as air interface material with refractive index at the monitoring equals 1.378 and 〖Ti〗_2 O_3 as a substrate interface material with refractive index at the monitoring equals 2.263. The thicknesses for these two layers are 165.076 and 94.024, respectively. Design ΙV is the second solution of Catalan analysis with the same materials like the first solution (Design III) but with different thicknesses. The thicknesses for these two layers are 88.887 and 60.311, respectively. All calculations for the layer systems were achieved using MathCAD linked to a well known electrical simulation program "PC1D". The simulation program showed enhancement for the