Theoretical efficiency of 63.2%, a breakthrough for third-generation photovoltaic cells!

Shocking! New Intermediate Band Solar Cells (IBSCs) can achieve a theoretical efficiency of 63.2%, three times higher than ordinary solar cells (with efficiencies in the region of 20%)! A breakthrough discovery by an international research team that may revolutionise the solar industry! Netizens are exclaiming: Is the IBSCs concept stock about to set off a boom?

The new darling of third-generation solar technology

Crystalline silicon solar cells represent the first generation of solar cells, including monocrystalline, polycrystalline and amorphous silicon solar cells. These cells are already widely used in commercial and residential applications and account for 90% of the global photovoltaic market. However, their energy conversion efficiency is only 15-25% and their production costs are high.

Second-generation thin-film solar cells are made on glass substrates, and although the materials and production costs are lower, their energy conversion efficiency is only 6-10%.

The third generation of solar cells aims to increase energy conversion efficiency, reduce costs and facilitate applications. They are known as new solar cells and include inorganic and organic thin-film solar cells, dye-sensitised and quantum dot-sensitised solar cells, and chalcogenide solar cells. Despite the relatively short development time of these cells, they have great potential for development because of their high theoretical energy conversion efficiency and relatively low production costs.

Among these, the intermediate band solar cell (IBSC) is a striking new concept for improving the global efficiency of solar cells. With a theoretical energy conversion efficiency of up to 63.2%, it is the new darling of third-generation solar technology and is increasingly favoured by the industry.

This increase in cell energy conversion efficiency is achieved by introducing a narrow energy band with a small density of energy states into the forbidden band of the semiconductor. The introduction of this narrow energy band allows for increased sub-band gap absorption while keeping the open circuit voltage constant. With this improvement, the solar cell absorbs most of the visible light in addition to some of the infrared light, thus increasing the current output and energy conversion efficiency of the cell.

Figure 1 Cell energy band diagram: conventional solar cells only have a conduction band CB and a valence band VB, but intermediate band solar cells also introduce an intermediate band (IB) to increase the absorption of sunlight

Despite the high theoretical energy conversion efficiency of the intermediate band solar cell (IBSC), its performance is not as high as expected due to its inherent high compounding nature (compounding of electrons and holes in the intermediate band) and the destruction of the semiconductor lattice, with the energy conversion efficiency being lower than the theoretical value or even lower than the efficiency of a typical cell. At the same time, the cell is very expensive to manufacture. In addition, IBSCs have short lifetimes and can only be used at low temperatures, which greatly limits their mass production and application.

Scientists from Imperial College in the UK and the University of New South Wales (UNSW) in Australia have recently announced the development of a new intermediate band solar cell (IBSC) and have published their latest research in the journal RRL Solar. The new design represents a major advance in the field of interstitial band solar cells. According to the report, the new IBSC uses a novel solar cell architecture and introduces a unique optical structure that effectively utilises more photons in the solar spectrum to increase the cell's photovoltaic efficiency. The publication of this research also marks an important step forward in the field of intermediate band solar cells, which is expected to promote the commercial application of intermediate band solar cells.

According to the researchers, the newly designed intermediate band solar cell (IBSC) introduces a new solar cell architecture that includes a 'ratchet band' (RB), the energy band of which can be seen in Figure 1. Room temperature operation is possible. This breakthrough will provide an important foundation for the future development of IBSCs cells and is a major milestone in the field of intermediate band solar cells.

Back in 2020, the two Spanish researchers had declared: "We believe that once efficient IBSCs have been developed, the scientific community will invest more effort in optimising the performance of these devices. We believe that once IBSCs prove to be very efficient and potentially cost effective, depending on the market segment, the industry will show a great deal of interest." Now that high-efficiency IBSCs are being developed, this could be a major reshuffle for the PV industry once more companies are involved in the development and mass production.