Novel vapor texturing method for EFG silicon solar cell applications

Abstract

This paper presents an acidic texturing and a novel vapor texturing method for Edge-defined Film-fed Growth (EFG) multi-crystalline silicon (mc-Si) wafers. P-type EFG mc-Si wafers with resistivity 0.5-2 Omega cm and thickness of 300 +/- 70 mu m were textured with acidic solution using HF:HNO3:CH3COOH. The reflectance decreased as the acid etching proceeded and then saturated when the etching depth reached 10 mu m. The isotropic etching of acid texturing resulted in minimum reflectance of 13%. For vapor texturing, the vapor particles were generated by adding silicon to HF:HNO3 acidic solution. Initially silicon was oxidized with HNO3 vapor particles. The nano-pore sized SiF62- ion formed over the EFG mc-Si wafer acted as a barrier on the Si surface. The HF vapor particles then dissolved the formed SiO2 effectively by passing through the nano-pores of SiF62- ion and etched the EFG mc-Si wafer. The anisotropic etching of vapor textured wafers resulted in an etching depth of about 2.78 mu m with reflectance of 5%. The EFG mc-Si solar cell fabricated with acid texturing had V-OC of 592 mV, J(SC) of 27.71 mA/cm(2) and efficiency of 12.85% while the cell with novel vapor texturing showed V-OC of 597 mV, J(SC) of 29.61 mA/cm(2) and efficiency of 13.54%. (C) 2012 Elsevier B.V. All rights reserved.