PERC deployment: The solar industry remains sweet on passivated emitter rear cell (PERC) technology, which continues to enjoy increasing production volumes thanks to its excellent cost-performance ratio, writes Corrine Lin, PV analyst at EnergyTrend.
Diminishing subsidies on a yearly basis have weakened the demand of the once booming photovoltaic (PV) markets of Greece, Spain, Italy and Germany. The focus of the PV industry is instead gradually moving to Asia. Currently, worldwide PV demand mainly comes from China, Japan and the United States. Together, they represent more than 60% of the worldwide PV demand in 2015. However, Japan and the United States will also reduce their renewable energy subsidies and may lose their positions as major PV markets after the next two years. Many countries chose to build large, utility-scale PV power plants when there were generous subsidy programs in place. As policies change and the utility-scale installation boom come to an end, steady demand increases in the rooftop markets will be critical to the future growth of the entire PV market. The latest statistical research by EnergyTrend, a division of TrendForce, indicates that the main export markets of Chinese PV modules stepped up their demand of high-efficiency products in the first half of 2015. High-efficiency PV product exports specifically targeted markets such as Japan, the United States, Europe and Australia. Among the various high-efficiency products, PV products based on passivated emitter rear cell technology (PERC) have the highest cost-performance (C/P) ratios and are the most competitive in the industry.
Figure 1: Major Markets for High-Efficiency PV Products in 1H15
Source: EnergyTrend Silver Member Report
The rise of PERC cells
The market demand of rooftop systems is linked to the power output of a PV module. Although technological improvement and production optimization of silicon wafers and conductive pastes have resulted in higher PV cell conversion efficiency over the years, products with higher C/P ratios and better efficiency are needed in the market to fulfill the rising demand of rooftop systems. Taiwanese PV manufacturers Sunrise and Gintech, for instance, have successfully mass produced PERC cells to meet this demand as well as creating a new trend in cell technology.
Various promising technologies had appeared through the history of PV industry, such as reactive ion etching (RIE), laser isolation, selective emitter (SE), laser doping, double print and dual print. Though each technology has its own supporters, they struggled during the mass production phase. Their products moreover have low C/P ratios due to low throughput or additional steps in the manufacturing process. Consequently, their popularity waned.
Compared with other technologies, PERC only requires to two extra manufacturing processes to the existing cell production – back passivation and laser grooving. The additional cost also does not exceed US$6 million for each production line. During mass production, each watt costs just an additional US$0.04 but there is a substantial rise in conversion efficiency. Due to these factors, Taiwanese manufacturers readily installed a lot of PERC equipment during 2013~2014, initiating a trend. Then in 2014, many global top-tier module makers announced they would raise their PERC capacities significantly. PERC technology has thus become this generation’s mainstream P-type cell technology.
Regional PERC capacity expansion
PERC capacity is expanding rapidly worldwide. EnergyTrend’s data shows global PERC capacity was about 2.5 GW at the end of 2014, and 1 GW of which were represented by Taiwanese PERC cells. However, Taiwan’s PERC capacity growth has slowed down by the second half of 2015. At the same time, the regional distribution of global PERC production has changed greatly as top global manufacturers such as Hanwha Q-CELLS, Trina, JA Solar and SolarWorld started increase their PERC capacities above 300 MW. By the end of 2015, they will raise the global PERC capacity to more than 7 GW, up 180% from 2014.
Figure 2: Comparison of PERC Capacity Allocation
Source: EnergyTrend Statistical Estimates
In 2014, manufacturers increased their PERC capacities by modifying Centrotherm production systems or trying out various solutions offered equipment providers such as Singlus, Levitech , Solaytec, and ASM. By contrast, manufacturers this year have chosen equipment that can successfully achieve mass production of PERC. As a result, equipment provider Meyer Burger became the biggest winner during the current wave of capacity expansion by offering the best solution available. However, PERC capacity is unlikely to increase significantly this year as Meyer Burger production system is in short supply. Mainstream equipment will remain fully booked by 2016, and manufacturers that are unable purchase Meyer Burger systems will find other ways to maintain their competitiveness. Some manufacturers may use plasma-enhanced chemical vapor deposition (PECVD) to create aluminum oxide (Al2O3) layer on PERC cells, while others will opt for atomic layer deposition (ALD) technology. Those manufacturers that are unwilling to take risks may also reconsider Eternal Group’s method, which is using current equipment with a unique alumina paste to bring out the effect of PERC rather than buying new equipment. All these different methods ensure PECVD will not be the dominant process.
Competition between multi- and mono-Si PERC cells intensifies
Aside from the choice of coating machines, the industry has yet to determine whether PERC will be mainly used in mono- or multi-Si PV products. From efficiency standpoint, a mono-Si PERC cell is 0.8~1% more efficient than a regular mono-Si cell, while a multi-Si PERC cell is 0.6% more efficient versus its regular counterparts. Hence, the mono-Si PERC has a slight edge in cell efficiency compared with the multi-Si PERC. Under the circumstance where costs are similar between mono- and multi-Si PERC cells, a manufacturer’s decision to go with either type will depend on the wafer specs, module price difference and end-market demand.
During the first half of 2015, Solartech, Inventec and TSEC have been selling multi-Si PERC cells at slightly lower prices than regular mono-Si cells. According to March and April prices, the average price of multi-Si wafer was around US$0.84/pc, and once these wafers were made into multi-Si PERC cells, their conversion efficiency was approximately 18.4~18.6%. Thus, wafers used for multi-Si PERC cells cost about US$0.188/W and can be assembled into 265 W modules. During the same period, the average price of mono-Si wafer was US$1.02/pc and its efficiency reached 19.4%. Wafers used for regular mono-Si cells therefore cost about US$0.22/W and can be made into 270 W modules. With a 5 W module efficiency difference and a near US$0.04 difference in terms of cell plus assembly cost, many module manufacturers would be more inclined to make multi-Si PERC products.
However, wafer prices have begun to change considerable since June because the mono-Si wafer market suffers weak demand and high inventory level. While the average price of multi-Si wafer maintains at US$0.82/pc, the average mono-Si wafer price has dropped from US$1.02/pc to US$0.95/pc. The price gap between mono- and multi-Si wafers has narrowed from US$0.18/pc to US$0.13/pc. Though mono-Si wafers have seen a significant price decline, EnergyTrend believes there is still room for further decrease as this market is relatively under-developed. Moreover, GCL, a leading multi-Si wafer manufacturer, plans to set up mono-Si wafer capacity at the end of this year. If the efficiency of multi-Si PERC cells does not grow notably in the future, EnergyTrend expects their market share will gradually be lost to regular mono-Si cells. Recent price data also shows an overlap between multi-Si PERC and regular mono-Si cell prices. This has allowed module manufacturers to purchase mono-Si cells at prices lower than multi-Si PERC cells as well as assembling them into modules with higher wattages. Many manufacturers of multi-Si PERC cells are aware of the situation and are searching for new technologies to maintain their competitiveness, such as RIE.
Figure 3: P-Type Cell Price Trend
Source: Based on data compiled by EnergyTrend.
Figure 4: Cost Price Comparison between PERC and Regular Cells
Source: Based on data compiled by EnergyTrend.
Rising PERC efficiency will delay N-type products from entering the mainstream
PERC has been a major technology to raise P-type cell efficiency. The pace of efficiency growth indicates that 300 W modules made up of 60 mono-Si PERC cells with 21% efficiency will become widespread at the turn of 2016 and 2017. Mono-Si wafer size may also upgrade from the current M1 to M2 by then. Not only 300 W will be the mainstream in the mono-Si PERC module market, cells in those modules will have their costs kept down at US$0.33/W or under. PERC in general will have a significant cost advantage compared with technologies for N-type cells that are capable of building a 60-piece, 300 W module (i.e. multi-busbar, smart wire, HIT, IBC and etc.).
Besides increasing efficiency, many cell manufacturers are also expecting raw materials costs for PERC cells to lower following the global PERC capacity expansion. The additional manufacturing cost can still fall from the current US$0.04/W. However, PERC’s increasing efficiency leads to a relative increase in light-induced degradation (LID), which is yet to be resolved. In the future, equipment providers will come up with new solutions to this issue in addition to reducing the boron oxygen complex, which acts as a harmful defect during the wafer production. Keeping LID under control will be crucial in determining if the PERC process can become the standard in cell production lines.
In conclusion, most top-tier manufacturers will implement a certain level of PERC capacity, and it is expected that the global PERC capacity will represent about 30% of the total global cell capacity by 2018. EnergyTrend furthermore projects that P-type cells will continue to dominate the PV market in the next two to three years owing to PERC technology. The PERC trend, however, will also push back the schedule for developing the next generation of N-type cells. For any high-efficiency N-type technologies, such as IBC or HIT, manufacturers are only going to add one or two production lines in their capacity expansion plans for the upcoming years. Therefore, N-type technologies will not be widely adopted until the pace of PERC efficiency growth has slowed down considerably.
*This article has been published in PV magzine issue 09/2015.
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