| Project Detail |
Investigating new materials to increase tandem solar cell efficiency
In recent years, selenium (Se) has become an attractive alternative to silicon in photovoltaic technology because of its suitably high band gap, high efficiency and ability to be processed at low temperatures. The EU-funded SeNTASC project will develop selenium absorber photovoltaic (Se PV) top subcell stacking with a high-efficiency Cu(In,Ga)Se2 (CIGS) bottom subcell towards long-term stable and high-efficiency tandem solar cells, using novel approaches in buffer layer band gap modulation and advanced hole-selective metal oxide layer modification to achieve an inverted bifacial Se PV. This approach will lead to an efficiency increase of approximately 10 % and establish Se as an excellent candidate for a top subcell in a tandem with high-quality CIGS solar cells, leading to a maximum theoretical efficiency of about 40 %.
Clean energy is crucial for a carbon neutral European continent, and wind, hydropower, geothermal, biomass, and solar energy conversion will generate hundreds of billions economic activity in the coming years. Among these, photovoltaics (PV) plays a crucial part in electricity generation directly transformed from sunlight. Recently, the efficiency of the dominant PV technology, Si, has reached over 26%, which is near the 29.4% theoretical efficiency limit for single-junction solar cells. In order to overcome this limit, the tandem concept that minimizes thermalization losses of photo-excited carriers has been successfully proven with multi-junction cells, where different band gaps are stacked in series. Over the past decades, the main challenge has been the lack of an efficient, long-term stable, low cost, and process compatible top sub-cell. Recently, selenium (Se) became an attractive option because of its suitable high bandgap , feasible process at low temperature, and reported efficiency.
This proposal (SeNTASC) aims at developing selenium absorber photovoltaic (Se PV) top subcell stacking with high-efficiency Cu(In,Ga)Se2 (CIGS) bottom subcell toward long-term stable and high-efficiency tandem solar cells by implementing novel approaches in buffer layer bandgap modulation, advanced hole-selective metal oxide layer modification, and finally achieving an inverted bifacial Se PV. The above-mentioned strategies will lead to ~10 % efficiency with open circuit voltage over 1 Volt with bandgap around 1.95 eV in an inverted superstrate configuration. Reaching these objectives, Se will be established as an excellent candidate for a top subcell in a tandem with high-quality CIGS solar cells. In this configuration, a maximum theoretical efficiency near 40% is expected. |
