Optimization of SiN x layer for solar cell using computational method

Abstract

SiN x film grown by using the plasma-enhanced chemical-vapor deposition is most-widely used for the conventional crystalline silicon solar cell as an anti-reflection layer and also passivates the surface and the bulk of the silicon wafer. To minimize the reflection loss and increase the efficiency of the solar cell, the thickness and the refractive index of the SiN x film is generally determined by analyzing the surface reflectance of the SiN x layer on the silicon wafer. On the other hand, we optimized the thickness and the refractive index of the SiN x layer by confirming the efficiency of the solar cell prior to the real manufacturing process of the cell. In this work, Silvaco TCAD tool was used to design the conventional solar cell and the thickness and the refractive index of the SiN x film were varied in the range between 50 – 90 nm and 1.8–2.2, respectively. The optimum values of the thickness and the refractive index of the SiN x layer on the non-textured silicon wafer were 70 nm and 2.0, which are somewhat different from those determined from the analytical calculation of the reflectance only. Also, Silvaco TCAD tool was used to investigate the passivation process of the hydrogenated SiN x film. Through the simulation of the hydrogen diffusion, reduction of the recombination rate of the photo-generated electron-hole pair in the cell was confirmed.