Design of Thin Films Removal on Solar-Cells Silicon-Wafers Surface

Abstract

In this study, the design of the mechanism of a recycling system using composite electrochemical and chemical machining for removing the surface layers from silicon wafers of solar cells is studied. The reason for constructing a new engineering technology and developing a clean production approach to perform the removal of surface thin film layers from silicon wafers is to develop a mass production system for recycling defective or discarded silicon wafers of solar cells that can reduce pollution. The goal of the development is to replace the current approach, which uses strong acid and grinding and may cause damage to the physical structure of silicon wafers and cause pollution to the environment, to efficiently meet the requirements of industry for low cost. It can not only perform highly efficient recycling of silicon wafers from discarded solar cells to facilitate the following remelting and crystal pulling process, but can also recycle defective silicon wafers during the fabrication process of solar cells for rework. A small gap width between cathode and workpiece, higher temperature, higher concentration, or higher flow rate of machining fluid corresponds to a higher removal rate for Si3N4 layer and epoxy film. Pulsed direct current can improve the effect of dregs discharge and is advantageous to associate with the fast feed rate of workpiece, but raises the current rating. A higher feed rate of silicon wafers of solar cells combine with enough electric power produces fast machining performance. The electrochemical and chemical machining just needs quite short time to make the Si3N4 layer and epoxy film remove easily and cleanly. An effective and low-cost recycle process for silicon wafers of solar cells is presented.