Spray-on solar cells could be a reality soon, thanks to a material called perovskite
Solar energy is getting more affordable by the day, and a new technology could really disrupt the field. Today, solar panels are made using silicon, but somewhere in the near future you could spray on or print solar cells directly onto surfaces!
Thanks to a material called perovskite, which includes a range of materials that could be used to harvest light when turned into a crystalline structure. Perovskites can be mixed in liquid solutions and could be deposited on a range of surfaces. This throws up a lot of possibilities of using this material to harness solar energy, in ways that traditional silicon made solar photovoltaic cells could find limiting. According to Bloomberg, one British company is planning to have a thin-film perovskite solar cell ready for commercial sale by the end of 2018.
Hiroshi Segawa, a professor with University of Tokyo, is leading a five-year project which is being funded by the Japanese govt., to propel the development of the perovskite technology. Even Japanese companies such as Panasonic and Fujifilm are invested in this. Segawa calls this technology as the front-runner for low-cost solar cell technology.
Advantages Perovskite offers over traditional solar PVs
Perovskite offers solutions to the limitations one faces with silicon based photovoltaic cells. Now while silicon is available abundantly, extracting it from sand is a process that requires a lot of energy. It takes temperatures as high as 1500-2000 degrees C to melt silicon dioxide in an eletrode arc furnace, which limits the production of silicon PV cells while adding to the greenhouse gas emissions from their manufacture.
Perovskite is a class of wide-ranging materials in which the organic molecules, made from carbon and hydrogen, bind with metals such as lead and a halogen such as chlorine to form a three dimensional lattice structure. Production of this is much cheaper than extracting silicon from sand. Manufacturers can use liquid solutions of perovskites and deposit a thin layer of it over surfaces of any shape. This also takes care of the rigidity aspect of the solar PV cells, which limits its use cases.
Perovskite is named after a Russian mineralogist Lev Perovski, and while its usefulness was discovered back in 2006, the structure was not well understood. Also back then, there was that thing with efficiency.
In terms of efficiency – the portion of sunlight that is converted into energy – the silicon photovoltaic cells still offer a better proposition, but perovskite technology is being improved on by top universities from around the world. From 2009, when the efficiency of perovskite was just around 4 percent, in 2016 that number has jumped to 20 percent – which is a 5x improvement in seven years. Efficiency for solar PVs has remained around 25 percent for the last 15 years. So perovskites is definitely more promising now.
In fact, the World Economic Forum has called perovskite solar cells as one of the top 10 emerging technologies of 2016.
According to professor Martin Green from the University of New South Wales, there are suddenly over 10,000 researchers working on perovskite now. Efficiency improvements are happening at quite a good pace, which makes the case for perovskite even more stronger. Green’s team achieved a 12.1 percent efficiency on a cell measuring 16 square centimetres – which is a record in itself. Smaller surfaces give higher efficiencies.
Possible use cases
Perovskite cells are being tested in multiple use case scenarios. For instance, one could use it on top of cars, windows, walls and so on. Oxford Photovoltaics has said that it will be developing thin-film perovskite solar cells to be printed directly on to silicon solar cells.
“Adding some time for qualification, certification and production, our first product could be commercially available towards the end of 2018,” said Frank Averdung of Oxford PV to Bloomberg.
Relevance for India
India is on the road to have as much as 100GW of solar energy by 2022. But this India Spend report points out why that target seems difficult to achieve.
“To achieve its targets, India must add 130.76 GW of renewable energy over the next six years, an average of 21.7 GW per year or, three times the capacity it added in 2016,” says the India Spend report. The report mentions weak infrastructure and lack of cheap financing as one of the main reason as being the main challenges.
Also in India, unlike in developed countries such as Germany, rooftop solar power project initiatives are not taken by citizens but only by large conglomerates or organisations. There is a lack of collectively pooling resources and using solar panels in a regular use case scenario – say atop a residential building. In Germany, around 51 percent of the installed renewable capacity is owned by individuals / citizens.
The costs associated with solar energy, though having fallen over the years, are still expensive than traditional means of generating power in India. Unless there are incentives given on that front, it is a potential lost.
The advantages offered by perovskite in this regard are too good to ignore. In fact, a researcher from Pune’s Indian Institute of Science Education and Research (IIESR) has been successful in producing stable, high-efficiency, all-organic perovskite nanocrystal solar cell with 10.77 percent efficiency.
It is not all a bed of roses for perovskite technology though. Solar PVs have been around for a while now and have proven their robustness. Perovskite researchers must first ensure how stable the material will remain outdoors for long periods of time. There has to be a method to ensure that the painting of the material is uniform so the coating is even.
Certification and testing of this technology to make it marketable can take some time. “You need someone to bankroll an operation to scale up to go into manufacturing,” said Green.
How soon we will see this spray-on / paint-on solar cell technology is anyone’s guess. But things definitely look promising.