Breaking PV cell efficiency records, driving down costs

Semiconductor component manufacturer, centrotherm photovoltaics, believes photovoltaic system costs could fall by around 20 percent by 2013, generating billions of euros of savings worldwide. In its drive to see this happen, the company has teamed up with researchers from the University of South Wales' Photovoltaics Technology Transfer Team in Australia to break two consecutive world records in solar cell efficiency.
Breaking PV cell efficiency records, driving down costs

Working with solar technology firm centrotherm, the team at the University of South Wales (UNSW) achieved a new world benchmark of 19.3 percent efficiency in May for a mass-produced, crystalline silicon solar cell. They then improved that result in June to advance the record to 19.4 percent. The previous record for cells created with this process was 18.9 percent.

Dr Matt Edwards, Program Manager of the Photovoltaics Technology Transfer Team in the UNSW School of Photovoltaic and Renewable Energy Engineering, said the records were achieved without exotic materials or equipment. "The exciting aspect of these records is that we achieved these results in a short time, using an industry-standard silicon wafer and modified industry-standard equipment," he said. "It’s another step closer to solar power costing the same as coal-fired electricity."

Dr Edwards said the gains, achieved on a standard p-type CZ silicon wafer, had produced a low-cost cell which delivered "the best bang for your buck" of any mass-produced cell in the world.

The record-breaking cells were produced using UNSW’s patented Laser Doped Selective Emitter (LDSE) process, which uses a high-powered laser and a light-induced plating process to create ultra-fine metal contacts on the cell surface, leaving more area exposed to light to create more power. One of the advantages of LDSE technology is its ability to boost cell efficiency with simple modifications to existing screen-printed solar cell production lines – the most common mass-production systems in use today. The process is already in pilot production at some facilities.

Dr Edwards said the group was now working on a new technology, double-sided LDSE (D-LDSE), which optimises both the front and rear surfaces of a solar cell to deliver efficiencies of up to 22 percent.

The new 19.4 per cent efficiency record was verified by the Fraunhofer ISE Solar Cell Calibration Laboratory and a paper detailing the work will be published in the inaugural edition of the Journal of Photovoltaics.

Driving down costs

Project partner centrotherm recently explained at Intersolar Europe in Munich (Germany) that advances such as that achieved by UNSW and solar value chain improvements are likely to reduce photovoltaic system costs by double digit figures within two years, leading to €1.6 billion of savings in Germany along, and more than €10 billion globally by end of 2013.

"More than one third of the cost reduction can be achieved through improved production processes covering the polysilicon, solar cell and modules stages", explained Dr. Peter Fath, CTO at centrotherm photovoltaics. Raw material costs, inverters, and installation predominantly comprise around two thirds of the cost saving. "System prices can fall by 20 percent to a net price of around € 1,930 per kilowatt by the end of 2013 if all other participants in the photovoltaic value chain, all the way through to the installation of the PV system, do their homework."

Higher cell efficiencies critical

A particular focus at centrotherm photovoltaics is on higher solar cell efficiencies, because these generate great cost-reduction potential. "We aim to have the 20 percent high-performance solar cell by 2013 at the latest – and specifically in mass production, and not only as a laboratory figure", Dr. Fath went on to comment. "Consequently, we will continue to push ahead with further developments at full speed." As a rule of thumb, a one percentage point higher efficiency cuts production costs by around six percent.

Higher production capacities that generate economies of scale comprise further drivers of lower manufacturing costs. This trend is particularly noticeable on the Asian market. Further additional significant cost effects are to be achieved by building an integrated factory that covers the entire solar value chain through the solar silicon production, solar cell, and solar module stages. This allows cutting out the margins of suppliers and other producers. "Already today, we can identify this as a trend among our premium cost leaders", as commented Dr. Fath of centrotherm photovoltaics, the pioneers of turnkey systems, and providers of key equipment along all important steps of the solar value chain.

"Solar electricity, which is already important, will receive a further significant boost to its cost appeal over the next few years, and become very attractive", noted Dr. Fath with a view to the future. Generation prices of 12 to 16 euro cents per kilowatt hour (kWh) will then be possible in Germany in around two years' time. With costs of seven to eight euro cents per kilowatt hour, a mix of renewable energies will achieve utility parity with conventional power plants by the middle of the decade. Wind and sun complement each other optimally in electricity generation, allowing storage capacities to be minimized.

"We see photovoltaics, in combination with other renewable energy sources, as making a key contribution to allowing Germany, as well as other countries, to realize an exit from the nuclear energy option", commented Robert M. Hartung, CEO and Management Board Chairman of centrotherm photovoltaics AG.

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