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within the thin single layer grating which has just two interfaces, results.
In order to enable a high slope efiiciency, a relatively low grating coupling coefficient of k ~ 3cm-1 was employed. The DFB laser, the same material without the grating and a reference FP laser were heated under continuous-wave operation by 20~30K. Results showed that the presence of the grating layer and the epitaxy processused in making the DFB laser only resulted in a very small increase in resistance as compared to the FP laser.
These recordresults show that with further modifications, the DFB is one to watch.
Source: Electronics Letters
ZSW break NREL 16year record with most efficient CIGS
Scientists in Stuttgart develop world record of 20.1% efficient thin film solar cell
The copper, indium, gallium and selenium (CIGS) solar cell was designed by researchers at Zentrum für Sonnenenergie-und Wasserstoff- Forschung Baden-Württemberg (ZSW). This breakthrough comes 16 years after research institute NREL first broke the record and should significantly improve the cost-effectiveness of CIGS thin-film photovoltaics over the medium term.
Board Member and Head of the Photovoltaics Division at ZSW, Dr. Michael Powalla commented,”This record is for thin-film technology in general and not just CIGS solar cells. A major factor in achieving this top position was the close cooperation between basic research at the university, applied research at the ZSW, and production development at our industrial partner Würth Solar.”
The 0 .5 square centimeter solar cell has a 64
www.compoundsemiconductor.net June 2010
total thickness of 4mm and was produced in a CIGS laboratory coating plant using a modified co-evaporation process, which in theory can be scaled up to a commercial production process.
The solar cell consists of the semiconducting CIGS layer and contact layers and the electrical and optical properties must be exactly matched when manufacturing the cell – a process that is extremely difficult to master. The new results have been verified by the Fraunhofer ISE in Freiburg, Germany.
The electrical power output is increased by higher efficiencies resulting in better financial returns. “Further up-scaling for industrial application is the next development step,” says Michael Powalla. However, it would take a while before the increased efficiency of CIGS solar cells can be commercially utilised.”
At a few microns thick, thin- film PV solar cells are much thinner than standard crystalline silicon solar cells and therefore more cost-effective.. The market share of thin- film photovoltaics has increased from 7 to approximately 17% in recent years.
Of the three basic variants of thin-film solar technology (amorphous silicon, CdTe and CIGS), with CIGS thin-film technology offering the highest efficiency.
Commercially available CIGS modules currently range from 10 to 12% percent efficiency. A complete module always has a lower total efficiency than a single solar cell. The new efficiency record shows the great potential of CIGS technology for lower-cost, efficient photovoltaic systems. Michael Powalla assumes that efficiency levels of up to 15% can also be achieved in commercial modules within the next few years.
The ZSW is an international leader in the development of CIGS thin-film modules. Together with the company Würth Solar, the institute has advanced this technology to enable industrial production. In 2006,
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