Researchers from the Electronics and Telecommunications Research Institute (ETRI) created an eco-friendly color Cu(In, Ga)Se2 (CIGS) thin-film for solar cells.

The eco-friendly color CIGS thin film solar cells developed by ETRI researchers. Source: Electronics and Telecommunications Research Institute (ETRI)The eco-friendly color CIGS thin film solar cells developed by ETRI researchers. Source: Electronics and Telecommunications Research Institute (ETRI)

The new solar cells, which are made by coating multiple thin films on a glass substrate, have higher absorption than other non-silicon based cells and also demonstrate high conversion efficiency and long stability. Creating these solar cells requires fewer raw materials, which means that they result in lower material costs. Likewise, the solar cells come in seven colors including purple, green and blue, at no additional cost or processing.

Initially, the new solar cells had one drawback: they were difficult to commercialize because the buffer layer was made of cadmium, a toxic heavy metal. To overcome this, the ETRI team replaced the cadmium sulfide buffer layer with zinc-based materials. With the new layer, the team achieved approximately 18% conversion efficiency, overcoming an obstacle to commercialization.

The team also created a new analysis method using photo pumping terahertz spectroscopy. This method improved the conversion efficiency of solar cells with zinc-based buffer layers.

The cells can be coated with a flexible substrate and a glass substrate that allows them to be bent, folded and expanded for applications in the next generation of solar cells.

A paper on the new solar cell technology was published in Nano Energy.