Solar cell manufacturing process for blocking back diffusion by using mask

Abstract

The invention belongs to the field of solar cell manufacturing processes, in particular relates to a solar cell manufacturing process for blocking back diffusion by using a mask. Before a silicon chip is diffused, a silicon dioxide or silicon nitride mask is prepared on the back side of the silicon chip, and a back side mask before diffusion prevents the formation of PN junctions on the back side in a silicon chip diffusion process, so that the problem of short circuits of upper and lower electrodes of the silicon chip can be solved directly, and edge and back side etching processes after diffusion can be eliminated. Therefore, losses such as cell damage, efficiency reduction and the like caused by edge etching are avoided. Moreover, passivation effect can be acted on the back side of the silicon chip when the back side of the silicon chip is masked, so that the photoelectric efficiency of a solar cell can be improved effectively, and the process is suitable for industrial production.

Description

technical field [0001] The invention belongs to the field of solar cell production technology, and in particular relates to a solar cell production process in which a mask blocks back diffusion. Background technique [0002] The traditional manufacturing process of solar cells is roughly divided into several steps such as texturing, diffusion, etching, dephosphorous silicon glass, anti-reflection coating, and screen printing. [0003] In the existing process of diffusing solar cells, a diffusion layer, ie, a PN junction, is inevitably formed on the periphery and the back edge of the silicon wafer. The diffusion layer on the periphery and the back edge makes the upper and lower electrodes of the battery form a short circuit. Any small local short circuit on the periphery will reduce the parallel resistance of the battery, increase the reverse current, and reduce the overall electrical performance of the solar cell. The surrounding PN junctions must be removed to avoid short ...

AI Technical Summary

Problems solved by technology

[0005] The plasma dry etching process is to etch the periphery of the silicon wafer through the alternating action of fluorine and oxygen under the condition of glow discharge. In essence, it is a kind of damage to the silicon wafer, which is easy to cause defects such as edge chipping and missing corners. In addition, plasma etching is prone to insufficient etching or excessive etching. The so-called insufficient etching means that the edge PN junction is not completely removed, which will cause poor electrical performance of the cell due to edge leakage.

The so-called excessive etching means that after the PN junction is removed, the etching is continued, so that the etching amount of the silicon wafer is relatively large, especially the etching amount on the front side (light-absorbing surface) of the battery is large, and the PN junction on the front side is destroyed, resulting in a relatively large loss of photocurrent. Large, so that the efficiency of the final cell is reduced

At present, in order to prevent the poor electrical performance of the battery sheet caused by insufficient etching, a slight excessive etching is usually used. Generally, the etching amount on the front surface is about 1-2mm from the edge, that is to say, the PN junction within 1-2mm from the edge on the front surface can be damaged by etching

[0006] The method of laser etching is to laser etch a groove at the front edge to achieve the separation effect of P-type and N-type. This method is relatively stable and rarely causes edge leakage due to insufficient etching. However, due to its etched groove It is located at about 100 microns to 500 microns from the edge of the front of the cell, which reduces the actual use area of ​​the front, which leads to a slight decrease in the efficiency of the cell, and the thermal damage of the laser to the silicon chip reduces the performance of the cell, so it is rarely used in industrial production.