By optimizing various manufacturing processes, ZSW (Zentrum für Sonnenenergie- und Wasserstoff-Forschung — or Center for Solar Energy and Hydrogen Research — Baden-Württemberg) in Stuttgart, Germany has raised the European record for copper indium gallium diselenide (CIGS) thin-film photovoltaic solar cell efficiency to 22% - just 0.3 percentage point behind the existing world record – as confirmed by Fraunhofer Institute for Solar Energy Systems ISE. ZSW had previously (in September 2014) raised its cell efficiency to 21.7% (which was, at that time, a world record for thin-film PV).
ZSW's latest cell has a surface area of 0.5cm2 (a standard size for test cells), and was produced in a laboratory coating machine using the co-evaporation method. "The technological potential is far from tapped out at 22% efficiency," says professor Michael Powalla, ZSW board member and head of the Photovoltaics division. "It will be possible to achieve up to 25% in the next few years," he believes.
A race between solar power technologies
CIGS technology overtook market-dominating multi-crystalline silicon technology in cell efficiency some time ago, extending its lead to a full percentage point. However, in module efficiency, silicon PV is still ahead (about 17% for commercially available modules, versus about 14% for CIGS modules).
Manufacturing costs amount to just 40 cents per watt even in small CIGS factories, and they can be slashed by expanding production capacity. Given an annual output of 0.5-1GW, CIGS PV plants can achieve 18% or greater module efficiency and costs as low as 25 cents per watt. So, costs can be brought down to a competitive level even at a relatively low output, it is reckoned, and it follows that CIGS PV manufacturing requires less upfront investment than silicon PV production.
Thin-film PV market opportunities on the rise
ZSW notes that the fact that thin-film PV modules deliver higher yields under low light conditions and are more shade-tolerant is a major selling point for people who own solar power systems. Also, it takes less energy to manufacture CIGS modules than silicon PV modules. Flexible versions featuring high-efficiency CIGS are also in the works.
The efficiency rates achieved in the southwest of Germany are also of interest to industry, ZSW adds. Industry partner Manz AG of Reutlingen, Germany recently decided to continue its commitment to CIGS and is developing the technology further in a joint effort with ZSW.
A record 52GW of solar power capacity was installed globally in 2015, and annual demand is expected to rise to more than 100GW in the next few years. This means that the new solar factories will be needed, notes ZSW.