Toledo Uni Scientists Make 6.4% Efficient Antimony Selenide Solar Cell

In a paper entitled ‘Influence of Post-selenization Temperature on the Performance of Substrate-Type Sb2Se3 Solar Cells’, published in the peer-reviewed journal ACS Publications (whose parent organisation is American Chemical Society), scientists working at the University of Toledo in the United States have developed a 6.43%-efficient solar cell using antimony selenide (Sb2Se3) films with favourable crystalline properties.

For achieving such a high conversion efficiency for this early-stage PV material, they focused on the selenization temperature. Although antimony selenide is not a well researched absorber material, it has a near-direct bandgap of ~1.2 eV and excellent optoelectronic properties, all the same. The scientists said that the cell they fabricated is “a low-cost and environmentally friendly device”, and was made by depositing the Sb2Se3 films on soda-lime glass substrates coated with molybdenum (Mo) using closed space sublimation (CSS). The latter is a physical vapor deposition process, and is common in the production of thin-films and cadmium telluride (CdTe) panels.

A bulk Sb2Se3 absorber layer was deposited using the source plate. The researchers explained that the obtained absorber layers were then selenized at temperatures from 350 to 450 degrees Celsius in argon at a base pressure of 10 Torr with 100 mg selenium for 30 minutes to promote the recrystallization of Sb2Se3. Upon the conclusion of this production step, the academics deposited a 55 nano-meter thick cadmium sulfide (CdS) buffer layer onto the absorber using chemical bath deposition. Then was deposited a front contact layer comprising a 50 nm high-resistive intrinsic zinc oxide (i-ZnO) layer and a 250 nm aluminum-doped zinc oxide (ZnO:Al) via radio frequency (RF) sputtering. Once all these layers were scribed together, they formed a solar cell with an active area of 0.2 cm². According to the scientists, the results of the experiment indicate that a proper selenization temperature is critical to achieving Sb2Se3 films with large grains, uniform morphology, high crystallinity, desired crystal orientations, and increased carrier density. They concluded that by optimizing the selenization temperature, they obtained Sb2Se3 solar cells with a power-conversion efficiency of 6.43%.

The authors of the paper include Suman Rijal, Deng-Bing Li, Rasha A. Awni, Sandip S. Bista, Zhaoning Song, and Yanfa Yan.