A Study Of ?-Si-based Solid Diffusion Source By Vapor Deposition For Preparation Of The Emitters Of Crystalline Silicon Solar Cells

Gaseous phase diffusion is commonly adopted in current PV industry for fabrication of emitters of silicon wafer-based solar cells. However, the uniformity of the emitter layers thus produced is known to be unsatisfactory, and the sheet resistance of the emitters is difficult to increase further beyond the current level achieved, which is believed to be required for further improvement of the solar cells. An alternative technique is proposed in the present work. The main idea is described as following. First, heavy-doped ?-Si-based films are deposited on the silicon substrate by hot-wire CVD. Then, diffusion under high temperature in the air and remove the rests by HF. In this thesis, the feasibility of the novel method is grasped and the recipe of the processing is designed by systemically researching the details about the materials and the depositing parameters of the diffusion sources, also the temperature, the diffusion time and the pre-treatment of the diffusion process. The main conclusions are as following:1) Depositing heavy-doped ?-Si:H film by hot-wire CVD as the diffusion sources can obtain good emitter, but it's difficult to remove the rests. While, controllable ?-Si:H film can. After ?-SiO_x:H film deposited by hot-wire CVD as the diffusion sources, the wafers are pre-treated at 400 ? in the air to remove the hydrogen in the films, then diffusion at high temperature in the air and remove the rests by HF. The uniform and controllable emitters without the rests can be obtained.2) To make phosphorus-doped emitter layer of the p-type c-Si solar cell, PH3 was used for the ?-SiO_x:H films depositing by hot-wire CVD. The sheet resistance in the range of 90²50 ?/? were obtained by adjustment of depositing and diffusion parameters. It is thought the method we raised may be good for p-type c-Si solar cell production for 90¹00 ?/? is an optimized range for nowadays solar cell production.3) To make boron-doped emitter layer of the n-type c-Si solar cell, B2H6 was used for the ?-SiO_x:H films depositing by hot-wire CVD. The sheet resistance in the range of 155⁶00 ?/? was obtained by adjustment of experiment parameters. The minimum value 155 ?/? for the sheet resistance is gotten with B₂H₆=8sccm,thickness of the ?-SiO_x:H=200 nm, for the Diffusion Source layer depositing and 1000 ?, 1 h for the diffusion process, which is suitable for the best sheet resistance of n-type c-Si.