Polysilicon solar cell production process and monocrystalline silicon solar cells almost, but the polysilicon solar cell photoelectric conversion efficiency will have to reduce a lot of its photoelectric conversion efficiency of about 17-18%. From the production cost, than the monocrystalline silicon solar cells to be cheaper, easy to manufacture materials, save power consumption, the total cost of production is low, so get a lot of development. In addition, the life of polysilicon solar cells than the monocrystalline silicon solar cells shorter.
Monocrystalline silicon solar cell production needs to consume a lot of high-purity silicon material, and the manufacture of these materials complex process, power consumption is large, in the total cost of solar cell production has exceeded one-half. Combined with the drawn single crystal silicon rod was cylindrical, sliced production of solar cells is also a wafer, composed of solar components, low utilization of the plane. Therefore, since the 80s, some countries in Europe and America has invested in the development of polycrystalline silicon solar cells. The center of gravity has been from single crystal to the direction of the development of polycrystalline, the main reason; can supply solar cells head and tail less and less; for solar cells, the square substrate is more cost-effective, through casting and direct solidification method Polysilicon can be directly obtained square material; polysilicon production process continues to progress, automatic casting furnace per production cycle (50 hours) can produce more than 200 kilograms of silicon ingots, grain size reached centimeters; due to nearly a decade of monocrystalline silicon The process of research and development is very fast, in which the process is also applied to the production of polycrystalline silicon cells, such as the choice of corrosion emission junction, back surface field, corrosive suede, surface and body passivation, fine metal gate electrode, using screen printing technology So that the width of the gate electrode down to 50 microns, the height of 15 microns or more, rapid thermal annealing technology for the production of polysilicon can greatly shorten the process time, single piece of hot process time can be completed within one minute, the use of the process in 100 square Cm polysilicon chip to make the battery conversion efficiency of more than 14%. It is reported that the battery efficiency produced on 50 to 60 micron polysilicon substrates exceeds 16%. Using mechanical engraving, screen printing technology in the 100 square centimeter polycrystalline efficiency of more than 17%, no mechanical groove in the same area on the efficiency of 16%, using buried gate structure, mechanical groove in the 130 square centimeters of polycrystalline Battery efficiency of 15.8%.
In general, the use of positive glue stripping process, deposition of Ti / Pa / Ag multi-layer metal electrodes, to reduce the metal electrode caused by the series resistance, often require thicker metal layer (8 ~ 10 microns). The disadvantage is that the electron beam evaporates to cause the surface damage of the silicon surface / passivation layer, so that the surface compound is improved. Therefore, in the process, the Ti / Pa layer is evaporated in the process. Another problem is that when the metal and silicon contact surfaces are large, the recombination speed of the minority will be improved. In the process, the use of a tunnel junction contact method, in the silicon and metal between the formation of a thin oxide layer (generally about 20 microns thickness) application of lower functional function of the metal (such as titanium, etc.) can be induced in the silicon surface Stable electron accumulation layer (also can be introduced into a fixed positive charge to deepen the inversion). Another method is to open a small window (less than 2 microns) on the passivation layer and then deposit a wider metal gate line (usually 10 microns) to form a mushroom-like electrode, using this method in a 4 cm2 Mc- Si on the battery conversion efficiency of 17.3%. In addition, Shallow angle (oblique) technology is used on the mechanical groove surface.
In the large-scale production of polysilicon batteries, a screen printing process is widely used. The process can be used for the printing of the diffusion source, the front metal electrode, the back contact electrode, the antireflective film layer, etc., with the improvement of the screen material and the improvement of the technological level , Screen printing process in the production of solar cells will be more common application.