Light redirecting film to improve heterojunction solar module performance

Finland-based Intelligent Control Systems Ltd. has presented a new light redirecting film that is reportedly able to improve the power yield of a heterojunction (HJT) solar panel by 3.8%.

Called Solar Energy Optics (SEO), the patented film is able, according to the manufacturer, to reduce losses in the edge area of heterojunction solar cells. “By applying the SEO film to the inside of the HJT module front glass, light is redirected from the less efficient edges into the more efficient regions of the cells,” the company said in a statement.

The new product is still not available for sale. “We have just entered into pilot production phase with our latest SEO film generation,” the company's CEO, Keimo Kalliosaari, told pv magazine.

The Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) tested the film on several panels based on different two different SEO configurations and M6 half-cut HJT solar cells with 1.7 mm cells and 2 mm string gaps. “The solar cells in the test were used out-of-the-box, without any additional modification or sorting,” the company specified.

According to Intelligent Control Systems, the test showed that the modules with the two different SEO architectures saw their power conversion efficiency increase by 0.66% and 0.75%, respectively, which it said corresponds to a 3.3 % and 3.8 % growth in power yield.

“The results show that the application of SEO film to a 120 or 144–cell module, with 2 mm cell gaps and a white backsheet, can provide an efficiency boost of 2.6 % relative improvement, or two power classes,” the manufacturer stated. “As an improvement on transparent bifacial modules or alternative to the gapless solution currently applied by some module manufacturers, the efficiency gains can exceed 3.5%.”