Aug
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Lead Free Hybrid Perovskite Research Grows Into Lighting
August 3, 2016 | Leave a Comment
Currently lead, a human toxin, is used in perovskite material preparations. Lead is nasty and the younger a human ingests it the more horrific the consequences. That means a product production facility using lead is going to be much more expensive to build and operate.
Lead-free, more efficient solar cells and other optoelectronics devices will likely be based on a family of materials known as hybrid perovskites. The VCU scientists have identified how to control different properties and stability in these solar cell materials using lead-free preparation. These new design principles identified super-ion building blocks, clusters of atoms that carry the same charge as the ions that they replace. The scientists can tailor these building blocks improve stability and other desired traits.
Scientists discovered how to control a material’s properties and stability to develop next-generation solar cells based on newly discovered hybrid perovskites (atomic structure shown above). Simulations revealed that hybrid perovskites could be viewed as super-alkali halides. The schematic illustrates a hybrid perovskite structure where the super halogens are the blue tetrahedrons, the metal atoms are green, and the alkali cation is in the middle (gray structure with pink and black atoms). Image Credit: The Royal Society of Chemistry. Click the study paper link above for more information.
These new design principles guided by simulations could lead to the next generation of solar cells and optoelectronics for lighting and data storage based on simple and environmentally friendly manufacturing methods.
Solar cell performance of hybrid perovskites has improved from under 4% efficiency in 2009 to over 20% efficiency today, but perovskite stability still limits the performance and today’s hybrid perovskites commonly contain lead.
The VCU led scientists performed simulations to fill the information gap in a series of lead-free hybrid perovskites, where experimental data were not available. Computational methods included density functional theory, ab initio molecular dynamics simulations, and dynamic crystalline lattice calculations.
The resulting material can be pictured as a super crystal composed of super-ions, both super-alkali and super-halogen ions. Changing the halogen (chlorine, bromine, or iodine) and metal (germanium or tin) in the super ions affected their ionic radii and the ionic nature of the bonding. The scientists identified design principles that correlated the ionic nature of bonding to the electronic band gap and other photovoltaic-relevant properties.
The team identified two methods to increase the ionic nature: using a smaller halogen to increase the radius ratio between super-ions and using a more metallic metal (tin compared to germanium). Also, they identified how the materials degrade when exposed to moisture and proposed counter strategies. This new atomic-level understanding could lead to the development of more efficient and longer-lasting solar cells.
Lead isn’t so much of a consumer threat when thinking of a solar panel outdoors. But when the research gets to lead free perovskites a whole field of lighting and other optical opportunities become highly interesting possibilities indoors. That potential is far larger than solar panels alone. Lets encourage these researchers – one big step at hand, lets hope more are coming.
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