King Abdullah University (KAUST) researchers have shown that 2D organic-inorganic hybrid materials possess fewer defects than their thicker 3D counterparts.
Today’s electronics rely on technologies that can develop almost perfect crystals of silicon; flawless to the atomic level. This is crucial because defects and impurities scatter electrons as they flow, which adversely affects the material’s electronic properties.
There is however a problem: Hybrid perovskites, an exciting class of electronic material, cannot be constructed using the epitaxial or layer methods developed for silicon. Instead, they are produced using solution-based processes.
According to the researchers, this no doubt makes them cheaper than silicon, but it also makes purity much harder to achieve than would be feasible.
Osman Bakr from the KAUST Solar Center together with colleagues from multiple divisions across KAUST and the University of Toronto, demonstrate that 2D layers of perovskite material can achieve levels of purity much higher than is possible than in their 3D counterpart.
“Two-dimensional hybrid perovskites are a subgroup of the big hybrid perovskite family,” explains Wei Peng, lead author and doctoral degree recipient from Bakr’s lab. “They can be derived by inserting large organic cations in three-dimensional perovskite structures.”
Hybrid perovskites are made up of lead and halide (such as iodine) atoms and an organic component. This class of materials in solar cells has already shown ground-breaking potential for energy conversion efficiency while having low production costs and the possibility for being integrated in flexible devices. This combination of qualities makes hybrid perovskites an exciting material for optoelectronic applications.
Peng, Bakr and coworkers created a 2D material made of periodic layers of hybrid perovskites with an organic component of either phenethylammonium or methylammonium. Using a solution-based fabrication method, the layers were placed on a gold electrode so the team could measure the electrical conductivity.
The KAUST measurements indicate that the 2D materials contained three orders of magnitude fewer defects than bulk hybrid perovskites. The team proposes that this reduction is because the large organic cations in the phenethylammonium suppress defect formation during crystallization.
The team then demonstrated the potential for their materials for optoelectronic applications by constructing photoconductors with high light detectivity. These results according to the researchers bode well for further advancements in designing and optimizing perovskite solar cells.
Image credits and content: KAUST/2017