In the field of photovoltaic technologies, silicon-based solar cells make up 90% of the market. In terms of cost, stability and efficiency (20-22% for a typical solar cell on the market), they are well ahead of the competition silicon cellular manufacturing manner.

however, after decades of research and funding, silicon-primarily based sun cells at the moment are close to their maximum theoretical efficiency. as a end result, new standards are required to attain a protracted-time period discount in solar strength prices and allow photovoltaic era to become a extra extensively adopted manner of generating electricity.

one solution is to vicinity two different styles of solar cells on top of every other to maximize the conversion of mild rays into electric energy. those "double-junction" cells are being extensively researched within the clinical network, but are high priced to make. now research teams in neuchâtel -- from epfl's photovoltaics laboratory and the csem pv-middle -- have advanced an economically aggressive answer. they've included a perovskite cell without delay on pinnacle of a general silicon-based mobile, obtaining a file performance of 25.2%. their manufacturing technique is promising, due to the fact it'd upload only some extra steps to the present day silicon-cellular manufacturing manner, and the cost might be affordable. their research has been published in nature materials.

perovskite-on-silicon: a nanometric sandwich

perovskite's particular properties have brought on a super deal of research into its use in solar cells over the previous few years. inside the space of 9 years, the efficiency of those cells has risen by means of a factor of six. perovskite lets in high conversion efficiency to be executed at a probably restricted production fee.

in tandem cells, perovskite enhances silicon: it converts blue and inexperienced mild greater effectively, even as silicon is higher at changing pink and infra-crimson mild. "with the aid of combining the 2 materials, we will maximize the usage of the solar spectrum and boom the amount of strength generated. the calculations and paintings we've finished show that a 30% performance should soon be possible," say the have a look at's most important authors florent sahli and jérémie werner.

however, developing an powerful tandem structure by way of superposing the 2 substances is no easy challenge. "silicon's surface consists of a sequence of pyramids measuring round five microns, which lure mild and prevent it from being reflected. however, the floor texture makes it hard to deposit a homogeneous film of perovskite," explains quentin jeangros, who co-authored the paper.

while the perovskite is deposited in liquid form, because it generally is, it accumulates inside the valleys between the pyramids even as leaving the peaks exposed, main to quick circuits.

a key layer ensuring an most beneficial microstructure

scientists at epfl and csem are becoming round that hassle by way of the usage of evaporation techniques to shape an inorganic base layer that absolutely covers the pyramids. that layer is porous, enabling it to preserve the liquid natural answer this is then introduced the usage of a skinny-film deposition technique called spin-coating. the researchers sooner or later warmth the substrate to a enormously low temperature of one hundred fifty°c to crystallize a homogeneous movie of perovskite on pinnacle of the silicon pyramids.

"till now, the same old method for creating a perovskite/silicon tandem cell become to stage off the pyramids of the silicon mobile, which reduced its optical homes and therefore its overall performance, earlier than depositing the perovskite mobile on pinnacle of it. it also added steps to the manufacturing procedure," says florent sahli.

updating existing technologies

the brand new sort of tandem cell is fantastically green and at once well matched with monocrystalline silicon-based technologies, which benefit from long-standing industrial knowledge and are already being produced profitably. "we are providing to apply equipment that is already in use, just including a few unique tiers. producers may not be adopting a whole new sun generation, however honestly updating the production lines they're already the use of for silicon-primarily based cells," explains christophe ballif, head of epfl's photovoltaics laboratory and csem's pv-middle.

in the meanwhile, research is persevering with for you to increase efficiency further and give the perovskite movie extra lengthy-time period stability. although the team has made a breakthrough, there may be nonetheless paintings to be done earlier than their era can be adopted commercially.