A solar cell barrier layer separates the materials that conduct electric current in the solar cells, protecting them from the negative impacts of oxygen, water and chemicals. To create barrier layers, manufacturers of solar cells use ternary (3D) nitrides, which contain three components: nitrogen and two metals. An alternative to three-dimensional compounds is the use of chemically active 2D forms, which often have higher electron (charge carrier) mobility. Electron mobility reflects the material’s ability to conduct current: the higher it is, the more efficiently solar panels convert light energy into electricity.
The scientists from the Ufa University of Science and Technology determined the properties of two-dimensional forms of zinc nitrides (with vanadium, niobium and tantalum) using computer modeling, after which they used quantum chemical methods to describe the distribution of electrons in the molecules and measured the mobility of these charged particles. The mobility of electrons in two-dimensional compounds turned out to be twice as high as in 3D forms. Moreover, electron mobility in a two-dimensional zinc nitride layer was at the same level as the highest known values of electron mobility in two-dimensional materials.
The authors also modeled the interaction of two-dimensional zinc nitrides with atmospheric gases: nitrogen, carbon dioxide, hydrogen, nitrous oxide and water vapor. The modeling showed that all three compounds – with vanadium, niobium and tantalum – are immune to the effects of nitrogen and carbon dioxide, but are also susceptible to degradation when interacting with ammonia and nitric oxide. Two-dimensional zinc nitride with tantalum showed the least resistance to ammonia and nitrogen oxide: it proved approximately two times less stable than the other samples. As a result, solar cells that use zinc nitride with tantalum as a barrier layer will last less than those that use zinc nitrides with vanadium or niobium.
“The two-dimensional monolayers under study have a number of characteristics required for their successful use as a barrier layer in solar cells. This includes high stability during exposure to atmospheric gases and high electron mobility. The study demonstrates new functional properties of nanomaterials that can be used to create high-performance photo devices,” Andrey Kistanov, project leader and candidate of physical and mathematical sciences, is quoted as saying by the Russian Science Foundation.
