Spread method of polycrystalline silicon solar cell

Abstract

The invention relates to a spread method of a polycrystalline silicon solar cell. The spread method is characterized in that the spread method comprises the following processing steps of entering a boat, warming, oxidizing, spreading, redistributing, cooling and going out the boat, wherein the spreading step comprises low temperature pre-deposition and then high temperature spreading. Reaction between a phosphorus source and a silicon wafer cannot be completed under low temperature, so that the low temperature pre-deposition is carried out on low temperature source communication at a first step of spreading, the phosphorus source cannot spread (or conduct spreading with low rate) inside a silicon wafer, the phosphorus source only accumulates on the surface of the silicon wafer, and a phosphorus film with certain thickness is formed on the surface of the silicon wafer after source communication for certain time; and the high temperature spreading is carried out on high temperature source communication at a second step, phosphorus on the surface of an original silicon wafer is reacted with the silicon wafer and spreads to the inside of the silicon wafer, and spreading rates of the center point and the periphery of the silicon wafer are same. Therefore, spreading uniformity is good, concentration distribution of impurities on the surface of the silicon wafer and inside the silicon wafer body is even, sheet resistance uniformity is improved, and final photoelectric conversion efficiency of a cell sheet is improved accordingly.

Description

Technical field [0001] The invention relates to a diffusion method of a polycrystalline silicon solar cell, belonging to the field of solar cell manufacturing. Background technique [0002] Solar cell is a device that directly converts light energy into electrical energy. Because of its cleanness, non-polluting, inexhaustible and inexhaustible use, it has received more and more attention. [0003] The diffusion of polycrystalline silicon solar cells is usually made by phosphorus diffusion. This step is a key step in the entire preparation process. Its quality will directly affect the photovoltaic conversion efficiency of the battery. The typical junction preparation is divided into two steps: the first step is to pass through with nitrogen. Liquid Phosphorus Oxychloride (POCl 3 ), the required impurity (phosphorus) is transported to the surface of the high temperature silicon wafer with carrier gas nitrogen (N2), and the impurity diffusion depth is about hundreds of nanometers; the...

AI Technical Summary

Problems solved by technology

Due to the small distance between silicon wafers in the diffusion furnace tube (about 2.5mm), it is difficult to obtain the same amount of phosphorus source at the center of the silicon wafer as the surrounding, resulting in poor diffusion uniformity, low impurity concentration at the center of the silicon wafer, and square resistance. On the high side, the final photoelectric conversion efficiency of the cell is low

It is difficult to change this problem simply by changing the temperature, concentration or time, and the degree of optimization is limited

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