Silicon Updates: New solar cells to capture entire spectral energy from the Sun

Solar energy is a major source of energy, where the technology is lagging to gain advantage of it. George Washington University (GWU) is known for its research in harvesting solar energy. A team of researchers from the university has recently developed a new solar cell prototype that is capable of capturing the entire spectral energy released from the Sun. The proposed prototype consists of multiple cells arranged in the form of a layers to construct a single solar cell.

GaSb-based solar cells

Based on efficiency, scientists working on solar cell are able to achieve 20-30% efficiency with the conventional solar panels. But with the new solar cells, 44.5% efficiency was achieved, an hence becoming the most efficient solar cell available. These latest solar panels use the panels called Concentrator Photo Voltaic (CPV) panels. These panels make the sun rays "concentrate" on to an array of micro-scale solar cells, with the help of lens. These micro-scale solar cells measure less than one square millimeter in area.
Different layers of this solar panel different energy levels from the respective wavelengths of the sunlight. In simple words to say, one-upon-another, these layers act as sieve for the sunlight. With the layer-arrangement of the cells, almost half of the energy is converted directly into electricity.

Around 99 percent of the power contained in direct sunlight reaching the surface of Earth falls between wavelengths of 250 nm and 2500 nm, but conventional materials for high-efficiency multi-junction solar cells cannot capture this entire spectral range. Our new device is able to unlock the energy stored in the long-wavelength photons, which are lost in conventional solar cells, and therefore provides a pathway to realizing the ultimate multi-junction solar cell. - Matthew Lumb, lead author of the study and a research scientist at the GW School of Engineering and Applied Science. 

Build of the CPV based solar cells:
These solar cells use the materials based on Gallium Antimonide (GaSb), which is conventionally used for the applications like infra-red lasers. The substrates based on GaSb act as the building blocks of the layers present in this prototype along with the solar cells based on conventional substrates. This arrangement helps to capture shorter wavelengths from the sunlight, when compared to the conventional solar cells. On the other hand, Transfer-Printing is another new technique used in this prototype to achieve three-dimensional arrangement of micro-scale solar cells with a high degree of precision.

Concentrated and High Concentration Photo Voltaic Prototypes

Economic aspects of CPV based solar cells:
When compared to the conventional solar cells, the cost for constructing these solar cells is high. The research team is working on reducing the cost of these cells. The primary objective of this prototype is to give a practical idea of achieving better efficiency when compared to the conventional solar panels.

CPV arrangement