New record in solar cell efficiency

US Department of Energy National Renewable Energy Laboratory (NREL) researchers have created a solar cell with 39.5% efficiency under illumination conditions equivalent to that of the Sun. This represents the highest efficiency ever recorded for any type of solar cell under real-world conditions.

Record efficiency for solar cells

The developed solar cell is based on an architecture known as inverted metamorphic multi-joint (IMM) and contains three junctions, components that generate electric current in response to light. Three of the connections are made of different materials, the upper gallium indium phosphide (GaInP), the middle gallium arsenide (GaAs) and the lower gallium indium arsenide (GaInAs) materials. This allowed the cell to capture more energy from the entire spectrum of light.

To achieve record efficiency, the researchers built the middle layer with “quantum wells”. By placing a conductive layer between two other materials with a wider bandgap, the team was able to confine electrons to two dimensions, allowing the material to capture more light. The middle layer’s inclusion of up to 300 quantum wells also greatly increased the overall efficiency.

The team says that while the current development is a significant breakthrough for solar cells, it is still quite expensive to produce this type of cell. Researchers are working on alternative cell designs that will drastically reduce the cost of manufacture and make the cells affordable for a variety of new applications.