New world record for CIGS solar cells

The document outcomes from a collaboration between the corporate First Photo voltaic European Expertise Heart (previously generally known as Evolar) and photo voltaic cell researchers at Uppsala College.

“The measurements that now we have made ourselves for this photo voltaic cell and different photo voltaic cells produced not too long ago are inside the margin of error for the impartial measurement. That measurement will even be used for an inside calibration of our personal measurement strategies,” says Marika Edoff, Professor of Photo voltaic Cell Expertise at Uppsala College, who’s liable for the research.

The earlier world document was 23.35 per cent (Photo voltaic Frontier, Japan), preceded by 22.9 per cent (ZSW, Germany). Uppsala College has held the document earlier than, the primary time being within the Nineties within the analysis collaboration Euro-CIS.

“At one time we additionally held the document for a series-connected prototype. Although it is fairly a very long time since we held the cell document, we have usually been simply behind the very best outcomes and naturally there are numerous related features to contemplate, such because the potential for scaling as much as a large-scale course of, the place now we have at all times been on the forefront,” Edoff says.

Photo voltaic cells are growing quickly worldwide and solar energy accounted for simply over 6 per cent of electrical energy across the globe in 2022 in response to the Worldwide Power Company (IEA). The very best photo voltaic modules of crystalline silicon, which is probably the most extensively used materials in photo voltaic cells, at the moment convert greater than 22 per cent of daylight to electrical energy and fashionable photo voltaic cells are each low price and secure in the long run.

One goal in photo voltaic cell analysis is to realize greater than 30 per cent effectivity with cheap manufacturing prices. The main target could be very usually on tandem photo voltaic cells, as being extra environment friendly, however to date they’ve been too pricey for large-scale use.

The world document of 23.64 per cent has been measured by the impartial institute Fraunhofer ISE in Germany. The scholarly paper presents a radical materials and electrical evaluation of the photo voltaic cell in addition to a comparability with earlier information for a similar sort of photo voltaic cell from different analysis establishments.

A photo voltaic cell’s most essential properties are the power to soak up mild and the power to move vitality to {an electrical} load. For this to succeed, the fabric should be capable to take up an optimum portion of daylight whereas avoiding losing this vitality by changing it into warmth inside the photo voltaic cell.

CIGS photo voltaic cells encompass a glass sheet product of regular window glass that has been coated with a number of totally different layers, every of which has a selected activity. The fabric that absorbs the daylight consists of copper, indium, gallium and selenide (therefore the acronym CIGS), with additions of silver and sodium. This layer is positioned within the precise photo voltaic cell, between a again contact of metallic molybdenum and a clear entrance contact. To make the photo voltaic cell as environment friendly as doable in separating out electrons, the CIGS layer is handled with rubidium fluoride. The stability between the 2 alkali metals, sodium and rubidium, and the composition of the CIGS layer are key to the conversion effectivity, i.e. the share of the entire photo voltaic spectrum that’s transformed to electrical energy within the photo voltaic cell.

When measurement institutes conduct their assessments, they measure the photo voltaic cell effectivity utilizing filtered mild that mimics the solar in each depth and spectrum. Throughout measurement, the photo voltaic cell is stored at a managed temperature and the impartial institutes commonly ship calibration photo voltaic cells to 1 one other. To be registered as a world document, an impartial measurement is required, which on this case was carried out by the measurement institute Fraunhofer ISE.

“Our research demonstrates that CIGS thin-film know-how is a aggressive various as a stand-alone photo voltaic cell. The know-how additionally has properties that may operate in different contexts, corresponding to the underside cell of a tandem photo voltaic cell,” Edoff says.

A number of superior measurement strategies have been used to additional perceive the correlation between the effectivity and the photo voltaic cell construction: materials from the photo voltaic cell has been characterised by nano-XRF (X-ray fluorescence spectroscopy) on the MAX IV facility in Lund, the place a cautious compositional evaluation has been made. Transmission electron microscopy (TEM) at excessive decision has been used to review cross sections of the photo voltaic cell, each composition as a operate of depth and the way the crystal grains are constructed up, in addition to the interfaces between the layers. Utilizing photoluminescence, the spectrum of the sunshine emitted by the photo voltaic cell after excitation by a laser has been studied as a method to understanding how effectively the photo voltaic cell takes care of electrons internally. A photo voltaic cell that shines brightly has a decrease share of inside warmth losses than a photo voltaic cell that shines faintly. Lastly, electrical measurement strategies have been used to analyse the doping of the CIGS materials.

“The truth that we now maintain the world document means loads for each Uppsala College and First Photo voltaic European Expertise Heart. For the CIGS know-how, which is understood for prime reliability, a world document additionally signifies that it might supply a viable various for brand new functions in e.g. tandem photo voltaic cells. That is essential for our analysis colleagues world wide. We hope that the analyses of the fabric and electrical properties will present a foundation for additional enhancements in efficiency,” Edoff concludes.