Researchers at the Swiss Federal Laboratory for Material Science and Technology have claimed to have achieved an efficiency of 22.2% for CIGS (composite of copper, indium, gallium, and selenide) flexible solar cells.

This is an improvement of 0.8% from the previous value of 21.4%, which was announced by the same lab. The current enhancement in efficiency is attributed to alloying the light-absorbing semiconductor layer to improve the electronic properties.

Scientists at the Swiss lab led by Shiro Nishiwaki modified the composition of the layer to improve the device performance and output voltage. The flexible solar cells are processed on a polymer film with the CIGS semiconductor layer that absorbs the light deposited by a low-temperature co-evaporation method. CIGS is a suitable absorber material for thin film photovoltaic owing to its thermo-chemical stability and high-power conversion efficiency.

“Two approaches explored to alloy the crystal delivered similar improvements in device performance,” said Romain Carron, group leader in Empa’s Laboratory for Thin Films and Photovoltaics. The team claims that the study findings can be transferred at an industrial scale following different implementations with equivalent outcomes.

The Swiss Federal Office of Energy (SFOE) supported the research, and the efficiency was independently measured at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany.

Flexible and lightweight solar modules manufactured using this technology are said to be suitable for applications on rooftops and facades of buildings, greenhouses, vehicles, airships, and portable electronics. Empa collaborates with Swiss company Flisom for roll-to-roll manufacturing of lightweight, flexible solar modules for such applications.

Recently, Japan-based Toshiba Corporation’s researchers announced a method of layering a transparent solar cell over a standard silicon cell to develop an efficient, low cost and reliable tandem solar cell to raise the solar module output.

In June, researchers from the Fraunhofer ISE’s Centre for High-Efficiency Solar Cells claimed a power conversion efficiency of 47.6% in a multijunction solar cell (III-V) using an anti-reflection coating at a concentration of 665 suns (heat concentration levels equalling 665 suns).