First Solar Inc of Tempe, AZ, USA has raised its world record for cadmium telluride (CdTe) photovoltaic (PV) research cell conversion efficiency from 21% (reported last August) to 21.5%, as certified at the Technology and Applications Center (TAC) PV Lab of Newport Corp. The latest record places First Solar ahead of its established research cell roadmap.
The record cell was fabricated at First Solar's manufacturing factory and Research & Development Center in Perrysburg, OH, using processes and materials suitable for commercial-scale manufacturing. The record has been documented in the US Department of Energy's National Renewable Energy Laboratory (NREL) 'Best Research Cell Efficiencies' reference chart. It is the eighth substantial update to CdTe record efficiency since 2011.
"Our latest research cell efficiency record is a result of continued learning in the material science and device physics of CdTe solar cells," says First Solar's chief technology officer Raffi Garabedian. The work is "in part a result of the many fruitful collaborations we have with academia, national labs, and our industrial partners, most notably GE Global Research," he adds. "The learning has enabled us to further optimize our fabrication processes and thereby boost the performance of practical devices further towards the theoretical limit."
The true value of improved cell efficiency comes from the translation of the science into commercially viable product with improved power output and energy density, says Garabedian. "By virtue of our adaptable thin-film manufacturing process and our dedication to science-based design-for-reliability, First Solar is unique in its ability to rapidly scale such new developments into cost-effective and reliable product," he claims.
Garabedian emphasizes that First Solar's sustained investment in CdTe technology development has enabled it to meet or exceed its aggressive projections for improvements in research cells and modules, as well as commercialized technology. In March 2014, the firm presented a technology roadmap anticipating a 22% research cell efficiency milestone in 2015. "Given the slope of our research cell improvements and the fact that it is still February, we remain confident that we'll meet or exceed our roadmap expectations," Garabedian says.
Atlas 25+ certification
First Solar also says that its focus on module durability is continuing to yield results for commercially available products. In late January, its production PV modules achieved Atlas 25+ certification status following a rigorous series of long-term combined-stress environmental exposure tests.
The Atlas 25+ certification stresses durability and degradation against accelerated environmental conditions experienced in long-term service. According to Azmat Siddiqi, senior VP for Quality and Reliability, First Solar modules passed the Atlas 25+ stress tests for all parameters, including power output, insulation resistance and visual damage in the hot/arid, subtropical, temperate and 'global composite' climate simulations.
"The modules were tested against the most stringent standards available," says Siddiqi. "Performance of our production modules is evolving hand in hand with other technology advances." Testing was conducted by Atlas Material Testing Technology, and formal certification documentation will be issued by SGS, an inspection, verification, testing and certification organization recognized for providing global benchmarks for quality and integrity, says Siddiqi.
First Solar says that the Atlas 25+ results and recent 1500V PID Free certification add to its list of extended module reliability accolades, which include what are claimed to be market-leading results in Thresher, Long Term Sequential and IEC 60068 Desert Sand Resistance tests that independently confirm suitability for sustained operation in the world's harshest climates.
