A multi-disciplinary team of scientists has shown that 2D organic-inorganic hybrid materials feature far fewer defects than thicker 3D versions.
Modern-day 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. But hybrid perovskites cannot be constructed using the epitaxial or layer methods developed for silicon. Instead, they are produced using solution-based processes. While this makes them cheaper than silicon, it also makes purity much harder to achieve as defect population and species are sensitive to the processing conditions.
Researchers from the KAUST Solar Center together with colleagues from multiple divisions across KAUST and the University of Toronto, demonstrated 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 the team. "They can be derived by inserting large organic cations in three-dimensional perovskite structures."
The team 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.
Their 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.
Next, the team demonstrated the potential for their materials for optoelectronic applications by constructing photoconductors with high light detectivity. These results bode well for further advancements in designing and optimizing perovskite solar cells. "A future in-depth study on how the defect formation is suppressed will help our understanding and benefit device performance-targeted materials engineering," says the team.