With global energy-related carbon dioxide emissions reaching an all-time high in 2021, the need for clean energy is greater than ever. Solar energy is one such alternative to fossil fuels. Solar cells have been created using various materials, but selenium (Se) is popular because it is inexpensive, stable, and non-toxic. Its efficiency, however, is limited by its low melting point and wide bandgap—the range in which no electron states can exist. Optoelectronics researchers have now overcome these constraints by alloying selenium with tellurium (Te), making selenium solar cells more appealing.
According to the researchers, the optimal bandgap range for single-junction solar cells is 1-1.5 eV, but Se’s bandgap is about 1.8 eV, making it less than ideal for use in solar cells. By combining selenium and tellurium, the researchers could tune the solar cells to the Shockley-Queisser limit, which is the maximum theoretical efficiency of a single-junction solar cell.
Alloying selenium with tellurium, which has the same crystal structure as selenium and a narrow bandgap, can tune the bandgap and raise the melting point, broadening the absorption spectrum and improving the quality of selenium solar cell films. As a result, the Se1-xTex alloy is expected to improve solar cell efficiency.