The new solar cell developed by the National Renewable Energy Laboratory (NREL) has broken a new record in conversion efficiency by closing in on 40% under the same lighting condition as sunlight.

The quantum well solar cell developed by the research team yielded a conversion efficiency of 39.5% under the same lighting condition as sunlight. In comparison, the highest conversion efficiency for common silicon solar cells and the emerging perovskite solar cells is mostly at 25%, while the tandem solar cell that has combined the advantages of the two aforementioned materials is now approaching 30% in efficiency.

The new solar cell has an IMM (inverted metamorphic multi-junction) structure, with three solar cell junctions inside that are indium gallium phosphide on the top, gallium arsenide in the middle, and indium gallium arsenide at the bottom. These three materials specialize in capturing light of different wavelengths that would facilitate additional power generation for solar cells.

Another factor that contributed to the new efficiency record is the quantum well at the middle layer that further binds the electrons within the flat area by placing the conductive layer in between the two materials that possess wider energy gaps, which allows materials to capture more light. The new solar cell has more than 300 quantum wells in the middle layer.

The research team emphasized on the fact that the statistics were generated under realistic conditions owing to how a lot of remarkable results in the past were achieved within a laboratory environment, where the highly concentrated illumination does not always faithfully represent the conditions outside of laboratories.

The NREL team also further tested the new solar cell on satellites and other aerospace fields, as well as its performance in space, which yielded an excellent efficiency of 34.2%. However, a high efficiency is followed by a high price, and the research team commented that the cost is still pretty significant for this type of cells, so a reduction in cost and expansion in applications are still essential for the next step.

 (Cover photo source: NREL)