In an attempt to develop high efficiency solar cells that can surpass polluting energy generating facilities in terms of amounts of electricity output, a team of engineers from Semprius Inc. and Solar Junction, together with scientists from University of Illinois, came up with a four-junction, four-terminal stacked solar cell, which has a 43.9 percent efficiency with a potential to exceed 50.
This high value is achieved thanks to a new material inside the cells that minimizes optical losses, and anti-reflective coating that ensures efficient transmission of light.
The unique multi-layer solar cell is produced following a micro transfer printing process, which allowed the team to stack together a triple-junction microcell with a single-junction one. The result, a four-junction, four-terminal solar cell, has the capability to capture light from a much broader spectrum range, while thanks to an anti-reflective coating, light is efficiently transmitted to all layers. The triple-junction cell within the stack captures all light with wavelengths lower than 1,300nm. If the light has longer wavelengths, up to 1,700nm, then it is passed through the single-junction germanuim cell, placed on the bottom.
The findings and full details about the incredible development appeared in Nature Materials. There, the authors explain the benefits and improvements that are introduced with the new strategy of high-speed, printing-based manipulation of microscale solar cells, and stacking them together with a new interface material placed between the layers.
Professor John Rogers, one of the authors of the study, lead scientist at University of Illinois and co-founder of Semprius, claims that although they reported an efficiency of nearly 44 percent, the incredible technology has the potential to easily exceed 50 percent.
To put the work in a context, last year Sharp reported the record efficiency of 44.4 percent, which was achieved using a system for concentrating the light onto the cell, however previous attempts to use microscale solar cells in the same set-up gave only 36.5 percent efficiency.
Specialists in the field conclude that there is definitely potential of the technology for large scale solar power generation using ultra-high efficiency solar cells.
Image (c) Nature Materials