Improvement of optoelectrical properties of silicon heterojunction solar cells by using ITO/SiOx DLARC with NH3 plasma treatment

Abstract

Silicon heterojunction (SHJ) solar cells have attracted significant interest due to their high efficiency and low temperature coefficient. Anti-reflective coating (ARC) is used to increase light absorption and short circuit current density (J_sc) of SHJ solar cell. Indium Tin Oixde (ITO) is commonly used ARC coating for SHJ solar cell because ITO has high conductivity and low resistance properties. To enhance the characteristics of the ARC, an additional transparent electrode with a lower refractive index than ITO was deposited. This increases the amount of light refracted into the solar cell, allowing for greater light absorption. This study focuses on enhancing the optical and electrical properties and J_sc by improving the ITO layer and ITO/SiO_x double layer ARC on the solar cell. Since SiO_x has low moisture stability and a refractive index is lower than 1.5, it is difficult to use it directly in solar cells. Therefore, NH₃ plasma post-treatment was applied to develop an ARC suitable for solar cell applications. Using RF/DC power sputtering for ITO and plasma enhanced chemical vapor deposition (PECVD) for SiO_x to make Double Layer of Antireflective coating (DLARC) and NH₃ plasma treatment. This structure increased transmittance from 86.73 % to 89.6 % between 300 and 1100 nm spectrum. This resulted in a higher J_sc of 39.85 mA/cm² and a conversion efficiency of 21.8 %. Both simulations and experiments demonstrated that ITO/SiO_x DLARC with NH₃ plasm post treatment structure offers superior anti-reflection properties compared to single-layer ITO coatings.