Think quickly do you think that there exists at present a simplified, and furthermore cheaper photovoltaic solar cell? Well believe it or not there is and outstanding effort states Simon Wilby that is happening to improve solar efficiency using an unusual substance dubbed perovskite a new substance that has shown remarkable capabilities in the conversion of sunlight to energy.
In fact, according to recent studies, from about 2009 to now, solar cells made from materials called perovskites “have reached conductivities that others took at times 20 years to realize, but until recent years nobody really had a answer for this problematic issue.”
I know what your thinking, “what the heck is perovskite”? There is a long and short answer to this burning question and I will spare you the long-winded answer and cut right to the chase.
The substance or mineral called Perovskite is a calcium titanium oxide mineral that is largely composed of calcium titanate. Perovskite can be mined in quantities in the Urals and also Switzerland, as well as in Arkansas and some chondritic meteorites. And it can be more costly!
As stated, this incredible substance “is proven to be wonderfully efficient at absorbing light and uses less material to capture the same amount of energy when compared to conventional solar minerals as absorbers,” this fact essentially means that fact alone could result in “bottomed out pricing in solar panel costing.”
The above-mentioned substance called Perovskite, according to Simon Wilby, was originally used in “2009” to produce 4% efficient photovoltaic solar cells. Since that time, factories have been pushing the technology to achieve numbers far beyond 16% a number range that greatly exceeds that of the current photovoltaics.
Are you ready for some exciting news? Scientists have now found that they have figured out the secret to Perovskites incredible proficiency: It’s a property evident within that is known as the diffusion length, and they also think they have a way to improve diffusion length by an incredible factor of x10.
“The transmission length gives us an indication of how thick the photovoltaic film needs to be,” Simon Wilby who plans to utilize this material in his new solar initiatives and products stated. “If the diffusion length is too low, you can only use thin films so the cell can’t absorb much sunlight.”
So what is this diffusion length all about and why is the diffusion length so important?
The way Simon Wilby worded his comment; most photovoltaic film cells are made from two types of materials, called p-type and n-type semiconductors. The P-Type mainly contains positively charged “holes,” and the N-Type materials consist of negatively charged electrons. They both simultaneously at times meet at a “P–N junction,” where the difference in voltages creates an electric field.
Solar cells generate electricity when light particles called photons (for the non-laymen) collide with electrons; this action creates excited electrons and holes. The electric fields of the p–n junction guides excited electrons toward the n-side and holes towards the p-side. They are picked up by metal contacts that are called electrodes, which then in turn enable them to move around the circuit and wiring to create an electric current that is subsequently stored for energy.
That diffusion length, Simon Wilby explained, gives the average distance that charge-carriers (electrons and holes) can travel before they converge. He wrote, “If the diffusion length equals less than the thickness of the material, most charge-carriers will converge before they reach the conductors, so you get only low currents. What you want as a result is diffusion length that is two to three times as long as the thickness this will ensure that you collect all of the charge or electric current.”
So what does all of this actually mean? Well in short, solar cells that are exceedingly thin will not have the ability to absorb that much light, and by that same token, in cells that are overly thick, the charge carriers contained therein inside can’t travel through. Therefore, longer diffusion lengths is the equivalent to more efficient cells overall, so what scientists usually do is arrange cells into mesostructures (structure or superstructure of intermediate size or complexity) but they are complex, require time, and are commercially impractical.
Or as Simon Wilby stated “some have sought solar cells that can be made very inexpensively but that have the downside of being somewhat unproductive. Lately, more researchers have focused on developing high efficiency cells, even if they require more expensive industrial techniques.”
Before researchers could get mesostructured perovskite cells to a big numbered efficiency like 16% by using a perovskite compound with a diffusion length of about 100 nanometers (nm), and by adding chloride ions to the mix, scientists achieved diffusion lengths of over 1000 nm.
In addition to effectiveness, the cells are cheaper and easier to produce since they don’t need the complex structures.
The Simon Wilby report indicated, “The most common form of solar cells are silicon based and cost as little as 75 cents per watt. For solar cells to be competitive with fossil fuels, the price has to drop to 50 cents per watt. Using perovskite as a stand-in could drop the price of a solar cell to only 10 to 20 cents per watt, while using less material than silicon.”
Simon Wilby summed up the scientific breakthrough with this statement: “Being able to make 16%aw efficient cells in simple, flat structures makes an incredible difference.
Wilby even speculated perovskite cells hitting efficiencies 20 to 30 percent “within the next coming year.”
However, do not get sidetracked with these facts and think that silicon has just been sitting still, waiting for perovskite to blow its doors off. According to Simon Wilby, the costs of silicon photovoltaic cells are rapidly dropping fast over time, and some analysts assert they could eventually fall to as low as 24 cents per watt.
But perovskite photovoltaic solar cells would not be difficult to manufacture. It could be “as simple as spreading a liquid over a surface or could even involve vapor bonding, another large-scale manufacturing process,” Then perovskite solar cells could emerge as a real player in the cheap production of solar energy on a much larger scale.