Widely used screen printing production of polycrystalline silicon solar cells - solar cells, process - screen printing industry, especially

Widely used screen printing production of polycrystalline silicon solar cells - solar cells

, process - screen printing industry, especially

Abstract: The large-scale development and use of photovoltaic solar power, photovoltaic cells to improve conversion efficiency and reduce production costs is the heart of the people on the solar cells in recent years further in-depth theoretical knowledge, improvement of production technology, IC technology penetration and the emergence of the new structure of the battery, the battery efficiency is greatly improved, large-scale production, the conversion efficiency of polycrystalline silicon cells have been close to the silicon solar cell, amorphous silicon cells in the stability problem is not made great progress, the polysilicon people pay attention to the battery, the world production is close to single crystal silicon, polycrystalline silicon solar cells this process the current development process and were from the laboratory scale production were compared in the system description. Introduction

1 We all know, there are many advantages of using solar energy, photovoltaic power generation will provide the main man Energy But the current situation, to make solar power a large market, is the general consumer acceptance and improve solar cell efficiency, reduce cost of production should be our overriding goal, from the current development of the international solar cell its development trend can be seen silicon, polycrystalline silicon, ribbon silicon, thin film materials (including microcrystalline silicon thin films, compound-based thin film and dye film). From industrial development, it has been the focus of single-crystal to polycrystalline direction, mainly due to; [1] the beginning and end of solar cell materials can supply less and less; [2] in terms of the solar cell, a square substrate is more cost-effective, by direct coagulation casting method and obtained direct access to a square polysilicon materials; [3] of polysilicon production technology continue to make progress, casting furnace automatic production cycle of each (50 hours) can produce over 200 kg ingots, grain size of up to centimeter level; [4] As the silicon technology of the past decade and has developed rapidly, in which technology was used in the production of polycrystalline silicon cells, such as selective etching the emitter, back surface field, corrosion suede , surface and bulk passivation, thin metal gate electrode, using wire Print Technology enables the gate electrode width down to 50 microns to 15 microns high, rapid thermal annealing technology for polysilicon production process can significantly shorten the time, single-chip thermal process time can be completed within one minute, using the technology in 100 square centimeters of silicon chip to make the cell conversion efficiency of over 14%. It was reported that 50 to 60 micron silicon substrate produced more than 16% cell efficiency. Mechanical groove, screen-printing technology in the 100 cm2 polycrystalline on the efficiency of more than 17%, no mechanical groove in the same area on the efficiency of 16%, with buried gate structure, machinery and groove in the 130 cm2 polycrystalline on cell efficiency of 15.8%.

The following two aspects of the polysilicon from the battery technology for discussion.

2. Laboratory efficient battery technology Laboratory techniques often do not take into account the cost of battery production and mass production can only achieve maximum efficiency of the method and means to provide specific materials and processes that can reach the limit.

2.1 on the absorption of light

Mainly for light absorption: (1) reduce the surface reflection; (2) to change the path of light in the cell body;

(3) using the back reflected. For silicon, method of application of anisotropic chemical etching in (100) surface produced textured pyramid-shaped, lower surface light reflection. But silicon crystal to deviate from the (100) surface, using the above method can not make even the suede, the current use of the following methods:

[1] laser groove Groove laser method can be produced in the polysilicon surface, inverted pyramid structure, in 500 ~ 900nm wavelength range, reflectance was 4 to 6%, with double-layer antireflection coating surface produced considerable.

At (100) reflection of silicon chemical production rate of 11% of the flock. Produced by laser textured surface than in the smooth double-layer antireflection coating film (ZnS/MgF2) short circuit current to increase by about 4%, mainly long-wave light (wavelength greater than 800nm) the reasons for slanting into the battery. Laser production of suede problem is in the etching, the surface damage caused by the introduction of a number of impurities at the same time, by chemical treatment to remove surface damage layer. Solar cells made by this method are usually higher short circuit current, open circuit voltage is not high, mainly due to the battery surface area increased, the recombination current increase.

[2] Chemical groove Application mask (Si3N4 or SiO2) isotropic erosion, acid etching solutions for etching solutions, but also for the higher concentration of sodium hydroxide or potassium hydroxide solution, the method can not be formed by the formation of anisotropic etching the kind of tip-like structure. According to reports, the approach down the face of the formation of micron spectral range 700 to 1030 significantly reduced reflex. But the mask layer will be formed at higher temperatures, causing decreased performance polysilicon materials, especially for lower quality polycrystalline materials, reduce the minority carrier lifetime. Application of the technology made of polysilicon in 225cm2 cell conversion efficiency of 16.4%. Mask layer screen printing method can also be formed.

[3] reactive ion corrosion (RIE) The method as a non-mask etching process, the formation of suede particularly low reflectivity in the spectral range 450 to 1000 micron reflectivity can be less than 2%. Only from the optical point of view, is an ideal method, but problem is serious silicon surface damage, the battery open circuit voltage and fill factor decreased.

[4] produced antireflection film For efficient solar cells, the most common and most effective way is to double-layer antireflection coatings deposited ZnS/MgF2, the optimal thickness depends on the thickness of the oxide layer below the surface and the battery characteristics, such as the surface is a smooth surface or suede, anti-reflection technology has evaporated Ta2O5, PECVD deposition Si3N3 so. ZnO conductive film can be used as anti-reflective material.

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