Nanocrystalline vs. Amorphous n-Type Silicon Front Surface Field Layers in Silicon Heterojunction Solar Cells: Role of Thickness and Oxygen Content

Abstract

We report on a systematical investigation of the influence of layer thickness and oxygen content of different silicon-based n-doped layers deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) on silicon heterojunction (SHJ) solar cell performance. N-type amorphous (a-), nanocrystalline (nc-) hydrogenated silicon (Si:H) and silicon oxide (SiOx:H) films were used as front surface field (FSF) layers on rear emitter (RE) SHJ solar cells. The benefit, both in electrical and optical properties, of using nc-silicon layers, is demonstrated. The best cell in the oxygen variation experiment was obtained with an (n)nc-SiOx:H FSF having a refractive index n of 2.72 at 633 nm, which leads to an increase in short circuit current density, jsc, of more than 1 mA/cm2 as compared to a reference cell with an a-Si:H FSF. This higher jsc obtained in our best nc-SiOx:H prototypes leads to a conversion efficiency, , of 21.4%. It is also remarkable our best cell result, certified by ISFH CalTeC, with an improved nc-Si:H FSF that enabled an improved jsc of 38.6 mA/cm2 and an of 22.5%.