III-V solar cells have a high conversion efficiency, with the highest efficiency already surpassing 43.5%, and now American scientists have broken a new record by achieving a 47.1% of efficiency for the new solar cell model, closing in on the 50% mark.
The significant achievement of III-V solar cell comes from its elements of group III, which consists of aluminum, gallium, and Indium, as well as elements of group V, which consists of nitrogen, phosphorus, and arsenic, containing excellent characteristics in optoelectronic conversion and electric transmission, making it a key semiconductor material for LED, optoelectronic industry, and communication technology. Despite being used by NASA on the exploration of Mars way back in the 50s, the application range of III-V solar cells has not been as extensive as to that of crystalline silicon solar cells due to the former’s relatively high cost.
The team of National Renewable Energy Laboratory (NREL) has developed a solar technology that is also of III-V variety, though this time it is a six-junction III-V solar cell.
Six-junction, refers to the six photoactive layers. As indicated by the press release, each layer is also constructed with multi-layered III-V semiconductors that are able to absorb the light from different spectral ranges, and scientists would integrate 140 layers of III-V semiconductors into a solar cell that is 1/3 the thickness of hair, where the conversion efficiency eventually reaches 47.1% under strong light.
That being said, the light intensity adopted by the research team in the laboratory was 143 times stronger than sunlight, and the conversion efficiency will reduce to 39.2%, if general daylight is used. Though the wow factor has declined considerably, the conversion efficiency of the cell still precedes to that of general crystalline silicon solar cells, and not to mention that this cell can also be applied on another optoelectronic technology. Ryan France, III-V multi-junction solar scientist, commented that this cell is optimal for concentrated photovoltaics (CPV).
Concentrated photovoltaics can be said as the newer generation of technology that possesses the advantages from both photovoltaics and concentrated solar power. The technology uses lenses and curved mirrors to focus sunlight onto the multi-junction solar cell at the bottom, and its conversion efficiency was transcended to 41.4% previously by European research association CPVMatch. France also pointed out that one of the solutions in lowering the cost of power generation is to reduce volume. Through catching and focusing lights with mirrors, one is able to decrease the materials for semiconductor, while also enhance the conversion efficiency.
Thus, the conversion efficiency of solar power may exceed the 50% mark, elevating the development of III-V solar cells. However, the internal resistance barrier of the cell that blockades electric current must first be resolved, together with lowering the cost of III-V solar cells for new market expansion, commented John Geisz, chief scientist of the NREL high efficiency crystalline silicon photovoltaics team.
(Cover photo is a sketch, source: Flickr/haru__q CC BY-SA 2.0)