Talk to the industry experts in Solar PV at the moment and it won’t be long until conversation gets onto the subject of perovskite. This solar cell component may be the new kid on the block, but it is proving to be a popular choice for research and development, potentially providing a much cheaper and more efficient alternative to silicon cells.
According to industry experts, it may have some way to go before it’s the main technology for solar but the perovskite structure could well help revolutionize the industry in the years to come.
What is Perovskite?
Naturally occurring perovskite was first brought to the attention to the scientific world when it was discovered in 1839 in Russia. Deposits have been found around the world in areas such Arkansas, Switzerland and in the limestone that was ejected when Mount Vesuvius erupted. The crystals have interesting electrical properties when they are exposed to a magnetic field which means they are useful in telecoms and microelectronics.
As far as solar PV is concerned, the slightly confusing thing is that it is the perovskite structure which is actually used in the cells. The term ‘perovskite structure’ applies to any material that has a similar type structure to calcium titanium oxide. There are many different kinds of perovskite structure and the difference between them depends on the spacing between the atoms and molecules which often dictates the uses that they are put to.
What is Perovskite Solar PV?
Solar panels that use perovskite cells depend on using what is called an absorber material which means it takes the heat and light from the sun and transforms it into an electric current. There are a number of different types of absorber but the most commonly used is methylammonium lead trihalide. There was initially some concern of the inclusion of toxic lead in these cells but this has been recently addressed when tin was used instead.
The Benefits of Perovskite Solar PV
Compared to silicon cells, perovskite is proving easier to process. Silicon needs to go through several stages to ready it for electricity generation which require high temperatures and the use of a vacuum – something that is problematic, if not insurmountable, on the industrial scale needed. Perovskite structures can be produced by a couple of different manufacturing processes that are potentially far more promising in respect of scale and sustainability.
The other benefit of perovskite is that it can be produced in a number of different forms, including thin film, which means that it could have a far wider range of uses than other minerals currently being considered for solar PV. One downside, so far, is that perovskite solar PV currently operates at lower efficiencies than silicon but this may well change as the technology develops.
Research into Perovskite Solar PV
Whilst we have known about the potential for the perovskite structure in electricity production for a few years now, it wasn’t until 2009 that researchers found that it could be incorporated into solar cell technology. The problem here was that it wasn’t terribly stable, lasting only a few minutes in some cases, and the power output was not particularly efficient, around 3.8%.
From then on, however, the fight was on to find a solution that stabilised the energy production and increased the efficiency. Current silicon solar PV is designed to last quite a long time, 20 to 25 years for most solar panel installations. In 2012, scientists at Oxford University found that they could make perovskite structure cells more stable with a solid state hole transporter, which also increased efficiency to around 10%. A lot has depended on exploring the architecture of the cells which operate in a different way to silicon, but the race is currently on across the world’s research establishments to find the most efficient and hardy combination.
The Future of Perovskite Solar PV
Finding an easy to produce and robust alternative to silicon has been on the minds of solar PV researchers for a while now. If the technology is to forge forward and become our energy production of choice then it needs to be cleaner, more easily manufactured and durable enough for the task we need it to perform.
Even over a short time we have seen increases in the efficiency levels of the perovskite cells since they were first used back in 2009 but there is still some way to go. In truth, the limited light to electricity conversion is unlikely to hamper future industrial development of the perovskite solar PV technology but its current instability, particularly in humid conditions, may well do.
It could well be used in more installations such as office window glazing panels because it can be produced in very thin films and this could also change the way we look at the deployment of solar in our homes and offices in the future. Oxford University are currently working on this and the eco magazine Nature has recently reported on areas where perovskite cells are already being used: “As with the coloured dye-sensitized solar windows recently installed in the SwissTech Convention Centre of the École Polytechnique Fédérale de Lausanne4, other highly efficient perovskite-based photovoltaic glazing panels could soon make their market debut.”
