- The solar cell is the key component in the whole solar energy system.
- Manufacturers with high-efficiency solar cells should win the competition.
- An absolute one percentage increase of cell efficiency could manage up to 30% cost savings for the whole PV system installation.
- Manufacturers have been expending a lot of effort for new cell efficiency improvement technology and commercialization though it may still take time.
Solar cell efficiency enhancement is another one of the key metrics for solar photovoltaic (PV) manufacturers, other than PV manufacturing capacity expansion which is the main task on most PV makers' schedule this year. Solar cell efficiency is, no doubt, the key differentiator for a PV manufacturer to win in the competition in terms of product superiority and cost effectiveness. This article will only talk about the crystalline silicon (c-Si) cell, which takes around 85% share of solar application at present.
The overview and status quo of solar cell efficiency
The first practical solar cell developed based on silicon substrate was of 6% efficiency in 1950s, and the solar cell was only used in space applications for the next two decades. The technology development and the PV market has not been progressing considerably until the mid 2000s when Germany solar PV market broke out by the stimulation of feed-in tariffs for renewable energy introduced by the German Renewable Energy Act. Today, the efficiency of mainstream crystalline silicon cell reaches around 17.5% and 19% for multi and mono type, respectively. The industry average efficiency evolution in recent years is listed below:
Multi c-Si (%)
Mono c-Si (%)
c-Si solar cell efficiency varies from different PV manufacturers, some of which develop proprietary technologies while others buy turn-key solutions. Here is a list of current commercial cell efficiency data from some of the top PV manufacturers,
Multi c-Si (%)
Mono c-Si (%)
Trina Solar (NYSE:TSL)
Canadian Solar (NASDAQ:CSIQ)
Yingli Green Energy (NYSE:YGE)
JA Solar (NASDAQ:JASO)
China Sunergy (NASDAQ:CSUN)
19.5% (QSAR II)
SunPower is definitely the industry leader in solar cell processing thanks to its consanguinity relationship with the semiconductor industry. To concoct high-efficiency solar cells is not difficult for SunPower, and the only challenge is to make it cost effective under competition from Chinese solar cell manufacturers. SunPower's Maxeon solar cell currently holds the world record with up to 25% conversion efficiency. Panasonic's HIT solar cell, acquiring and rebranding from Sanyo, is the second leading efficient cell next to SunPower. The technologies of SunPower Maxeon and Panasonic HIT are unique, different from each other and distinct among other conventional solar cell processing technologies adopted widely by Chinese PV makers. There is no uniform solar cell technology development roadmap in the solar industry, which is a major weakness and reason for push back in industry evolution, comparable to the semiconductor industry. The famous Moore's law applied in the semiconductor industry has proven to be the guidance for the industry's effort in long-term planning and research and development targets, while lacking of such a law in the solar industry has diversified the resources and energies to push forward solar cell technology.
Cell efficiency is the key cost down driver
For solar PV power generation, people are concerned about the hard cost of PV module manufacturing, including raw materials and processing expense, which is important, of course, to lower the system cost directly. With the polysilicon price stable or even moving upward a little recently while non-silicon cost reduction falls, the cell efficiency enhancement is to be the key cost down driver. Assuming multi c-Si cell efficiency is up to 18.5% from the current 17.5%, a 5.7% increase, the cost of the same size PV module (e.g., 60 pieces of 156x156mm cell) will decrease by 5.9% directly and will definitely lead to cost savings of transportation, land, installation and balance of system (BOS), all of which contribute to a decreased levelized cost of energy (LCOE) for solar power generation. An absolute one percentage increase of cell efficiency could manage up to 30% cost savings for the whole PV power system installation.
The outlook on solar c-Si cell
National Renewable Energy Laboratory (NREL) has a famous trustworthy Best Research-Cell Efficiencies roadmap, which indicates that the solar cell efficiency ceiling of multi and mono crystalline silicon is 20.4% and 25%, respectively. Theoretically, the room for solar cell efficiency increases will be about 10% to 20% under the circumstance of a non-concentrator application if no disruptive technologies happen.
With visible profitability since the second half of last year, many PV manufacturers started intensifying cell development. For example, SunPower Fab 4 is under construction for its next generation cell technology and will lower its module cost up to 35%. Most Chinese PV makers have been working with PV research institutes worldwide to strive hard for solar cell efficiency improvement, but commercial mass production remains a challenge due to CapEx availability and workmanship maturity. Here are a bunch of recent PV crystalline cell efficiency breakthrough announcements:
- Panasonic Corporation announced that it has achieved a conversion efficiency of 25.6% in its HIT solar cells.
- Trina announced that it has developed a new high-efficiency Honey Ultra monocrystalline silicon module with a new record of 326.3W, which has been independently certified by TUV Rheinland. The Honey Ultra cell used in this module has an industry-leading efficiency of 24.4%.
- China Sunergy announced that its mono-crystalline solar cells have reached 20.26% conversion efficiency in the pilot line, and have received certification from Fraunhofer ISE.
- JA Solar announced that its multi-crystalline silicon solar cells have surpassed 19% conversion efficiency, and JA Solar plans to commence mass production of its new multi-Si cells and integrate them into module assembly lines for commercial use in the second half of 2014.
- JA Solar announced that its p-type mono-crystalline silicon solar cells (PERCIUM) have surpassed 20% conversion efficiency, which has been independently confirmed and certified by Fraunhofer ISE.
As the mainstream solar PV product, the c-Si cell is the key high-tech component in the whole value chain and the decisive factor for PV manufacturers to compete in the industry. The superior cell efficiency will help PV makers stand out in terms of corporate branding, business coverage and cost competitiveness. To lower the PV system cost by increasing cell efficiency is significant when cost of manufacturing materials is hardly to be reduced more. While c-Si cell efficiency is getting close to the theoretical limitation, we are eager to see any disruptive technologies that would boost the solar cell efficiency further and the potential winners in the PV industry would be those who master the technology and fulfill it in mass production.
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