March 09, 2017 Source: Photovoltaic News

      Recently, the Fraunhofer ISE (Fraunhofer ISE) successfully increased the efficiency of polycrystalline cells to 21.9% through the N-type technology such as TOPCon, once again breaking the industry-recognized polycrystalline cell efficiency by 20%. The limit value is also higher than 19.6-19.8% of the mainstream single crystal and "single crystal + PERC".

In order to further reduce the back recombination rate, achieve the overall back passivation, and remove the back film opening process, passivation contact technology has become a hot research topic in the industry in recent years. TopCon (Tunnel Oxide Passivated Contact) structure does not require back opening and alignment, and does not require additional local doping process, which greatly simplifies the battery production process, improves energy output, and has room for further improvement of conversion efficiency, or can be The entry point of a generation of industrialized N-type high-efficiency batteries. TopCon technology is pushing the efficiency of polycrystalline cells to 22%, and the previous "polycrystalline battery efficiency limit is 20%" is not broken.

Polycrystalline technology, which accounts for 80% of the crystalline silicon market, has always been the focus of major manufacturers. According to the ratio, the cost of polycrystalline electricity is reduced by 1 cent, and the electricity cost of the entire crystalline silicon photovoltaic industry can be reduced by about 8 cents. Its market influence and driving force are unmatched by other technical routes. After the two years before the single crystal completes the promotion of diamond cutting, shrinking and polycrystalline cost performance, the polycrystalline diamond wire cutting silicon wafer is about to be mass-distributed, the unit output is increased, the auxiliary material consumption is reduced, and the cutting cost can be reduced by about 0.4. ~ 0.6 yuan / piece. At the same time, the black silicon texturing technology matched with the diamond wire cutting is also mature, and various polycrystalline manufacturers have announced that they have already mass production. Compared with the conventional silicon wafer products, the conversion efficiency of the black silicon wafer can be increased by 0.2%-0.4%, and the output power of the component (60-piece type) can be increased by about 5 watts.

Thanks to the promotion of many first-tier manufacturers, the application of PERC (Passivated Emitter and Rear Cell) technology on polycrystals has also matured. It has been reported that PERC technology can increase the efficiency of single crystal cells by 1%, while polycrystals can only increase by 0.5%. However, data from first-tier manufacturers such as Artes and Hanwha show that the use of PERC technology can increase the efficiency of polycrystalline cells by 1%, and Hanwha can even increase by 1.2%. At present, the conversion efficiency of high-efficiency polycrystalline cells can reach 18.6%, superimposing 0.4% black silicon texturing gain, and then superimposing 1% PERC technology gain, 18.6%+0.4%+1%=20%, "Golden wire cut + black silicon + PERC "Technology can promote multi-cell battery mass production efficiency of 20%, can fully package 290W (60 pieces) high-efficiency components, polycrystalline will enter the "super-runner" era.

The future development of photovoltaic technology still depends on the potential for cost reduction and efficiency. After decades of development, P-type Czochralski single crystal technology has not been fundamentally broken, and its potential has been exhausted in the past two years. Relatively speaking, polycrystalline first-line manufacturers are promoting large-scale diamond-cut matching black silicon cashmere and PERC battery technology, which will lead the existing ultra-large-scale polycrystalline products with more than 50 GW of polycrystalline capacity and market share of nearly 80%. Reduce costs and improve efficiency. It is worth noting in the future that cutting-edge technologies are ingot single crystals and N-type single crystals. The conversion efficiency of ingot single crystal is close to P-type Czochralski single crystal, only 0.3% difference, but the cost is 10% lower than P-type Czochralski single crystal, the production capacity is doubled, and the industrialization trend has been formed; N-type single crystal is more P The single crystal has the natural advantages of high lifetime, low photo-induced attenuation, and has a larger space for efficiency improvement. At the same time, the N-type single crystal module has the advantages of low light response and low temperature coefficient, so it has high power generation and reliability. The high double advantage is the mainstream direction of the future development of the single crystal industry, but the current relative cost is relatively high.

Constantly pursuing cost reduction and efficiency improvement and reducing the cost of photovoltaic power generation is an eternal theme of the photovoltaic industry. According to industry authority forecasts, by 2025, high-efficiency polycrystalline, ingot single crystal and N-type single crystal will develop into a market ratio of 6:2:2. At that time, photovoltaic power will certainly achieve parity on the power generation side, like today's coal. Electricity and water and electricity go into thousands of households.