Finland-based optical solutions company ICS Intelligent Control Systems Ltd announced during a test at an approximately 3.8% increase in performance achieved with Heterojunction (HJT) solar modules combined with its patented Solar Energy Optics (SEO) light redirection film Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE).

The emerging HJT solar cell technology can achieve higher efficiencies than traditional c-Si cells and even cells processed with PERC techniques. But the problem of power loss in the edge area of HJT cells has long been an obstacle to unlocking the optimal efficiency of these cells. By applying ICS’ SEO film to the inside of the HJT module’s front glass, light is redirected from the less efficient edges to the more efficient areas of the cells.

During testing at Fraunhofer ISE, four half-cut HJT M6 solar cells with 1.7mm cell and 2mm string spacing were assembled into modules with two different SEO foil configurations, overlapping the cell edges by 0.5mm and 1mm, respectively. The solar cells in the test were used in their original state without any additional adjustments or sorting.

The results showed a significant improvement in both maximum power and fill factor. An absolute increase in module efficiency of 0.66% to 0.75% was achieved, which corresponds to a relative improvement of 3.3% or 3.8%.

The improved performance is a result of the combination an increased solar cell efficiency by minimizing edge recombination losses and an improved utilization of light from inactive module areas.

According to ICS, detailed optical simulation models of the solar panels and the SEO film were constructed and validated with experimental data. The results show that applying SEO film to a 120 or 144 cell module with 2mm cell spacing and white backsheet can bring an efficiency increase of 2.6% relative improvement or two power classes. As an improvement over transparent bifacial modules or as an alternative to the gapless solution currently used by some module manufacturers, efficiency gains can exceed 3.5%.

“These new results demonstrate that overlapping the edges of heterojunction solar cells with SEO film has the potential to change the game for high-efficiency PV modules,” said Dr. Andrea Pfreundt, product manager at ICS.

“We offer a manufacturable solution with an additional Wp cost well below the regular module cost for residential and utility formats,” said Kari Rinko, CTO of ICS.