Formation of a Porous Silicon Layer by Electrochemical Etching and Application to the Silicon Solar Cell

抄録

SiN_x thin film grown by plasma-enhanced chemical vapor deposition (PECVD) has conventionally been used as an antireflection layer of the silicon solar cell. In this work, a porous silicon (PS) layer formed by electrochemical etching was shaped on the surface of a crystalline silicon wafer for a simple alternative of anti-reflection coating (ARC). The etching solution was prepared by mixing HF and ethanol for efficient bubble elimination on the silicon surface during the etching process. The anodization of the silicon surface was performed under a constant current, and the process parameters, such as current density and etching time including volume fraction of HF to ethanol in the solution, were carefully tuned to minimize the surface reflectance of the CZ silicon wafer with sheet resistance of 35-40 Ω/□. The PS layer as an anti-reflection coating in the solar cell was compared with conventional PECVD SiN_x thin film by measuring the surface reflectance of the cell. Also, Photovoltaic I-V properties and the quantum efficiencies of the cells with PS layers were measured.