Concept
Solar cells have yet again gone through some significant changes warranting a new milestone in efficiency. Researchers, led by Dr. Henry J. Snaith, from the University of Oxford, Toin University of Yokohama and the National Institute of Advanced Industrial Science and Technology (both in Japan) have co-authored a paper detailing how the have achieved a record efficiency of 10.9% conversion rate by downgrading their material make-up. Perhaps it’s not exactly a downgrade per-se but rather using more common materials rather than rare-earth compounds. The materials that make up the cells electrode are the key factor in gaining conversion (photons to electrons) efficiency. These differ through the various kinds of the cells themselves with the most popular being TiO2 (Titanium dioxide) which is mainly used in solution-processable solar cells. In order to increase the efficiency of those cells, the researchers needed to find a way of overcoming the energy-loss associated with the ‘photogeneration’ (photon absorption by silicon and the energy transferred to an electron-hole pair) of the excitons (charge carriers). The researchers found that if they replaced the titanium dioxide with alumina (Al2O3) they could overcome the problem of energy loss as alumina is a ‘wide-band gap insulator,’ which prevents electron bleed-off and acts as a meso-scale scaffold (conduit) that forces the electrons to the cells perovskite (crystalline structured material) ETA layer thereby increases the cells conversion efficiency (up from 8%) as well as lowering the cost of manufacturing the cells themselves. It’s the researchers hope that the cells efficiency can be increased by experimenting with different semiconductors or perovskites to increase the solar cell’s absorption rates.
North Caroline State University Nano-Flower.
Energy efficiency doesn’t have to be all about bland silicates, however as researchers from North Carolina University have created a rather striking ‘Nano-Flower’ that may increase next-gen lithium ion capacity and efficient solar cells. The research team, led by Dr. Linyou Cao (assistant professor of Materials Science and Engineering), created the nano-flowers using germanium sulfide (GeS- which is a semiconductor material). The flower-like structure has an enormous surface area while only using a tiny amount of space which could lead to highly efficient supercapacitors that can hold significantly more energy. In order to create the nano-flowers the team heated GeS powder until it vaporizes inside of a furnace. The vapor is then pushed into a significantly cooler region of the furnace where the gas eventually settles into a 20 to 30 nanometer thick sheet (up to 100 microns long). As more of the gas is cooled they form tiny crystalline sheets that branch out from one another forming the flower-like appearance. Dr. Cao states that the key to the formation lies with controlling the GeS gas so that it produces sheets rather than being clumped together. The properties of GeS are similar to that of graphite in terms that it forms neat ordered layers of materia,l but unlike graphite the atomic structure of germanium sulfide make it ideal to absorb photons and turn them into energy. It’s also super cheap as well as non-toxic, making it ideal for inclusion into green technology.
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