Last edited: 21:56, 10 January (EST)
In the world of photovoltaic cells, the rise of perovskite solar cells is exciting. It may not be immediately obvious, but to those who know the development of efficient and productive solar cells, this new compound used in the structure of solar cells provides an insight into how the world can achieve better energy efficiency.
Initiatives like the American SunShot Initiative, spearheaded by the Department of Energy, are pushing research and development firms to find new ways to improve the functionality of solar energy. The SunShot Initiative drives companies to make solar energy as competitive on the market as traditional energy source without the need for subsidies to boost its appeal. That’s a big ask considering that most solar cells don’t operate as efficiently as they could to achieve these lofty goals.
So, that’s why the introduction of perovskite, a crystalline-structure that has more efficient light-absorbing layers in the compound excites those in this energy field. It’s changed the way scientists and researchers think about photovoltaic cells and how to layer better cells to meet the growing energy needs of the world. Does the perovskite solar cell hold the answer? Let’s examine how it performs against other methods of solar energy capture.
The perovskite solar cell was only first introduced in 2012 for consumer products at around 10% efficiency (see the chart below, click to enlarge). Its initial discovery was fairly low on the efficiency scale, just hovering around 4%. That was just a mere 5 years ago.
That number isn’t too bad as an introduction considering many other, already tested methods of solar energy capture were performing at an average of 14%, with the highest at the time capturing 24% of the energy it was exposed to.
But what’s really exciting about the developments this year was the jump to a staggering 22% on its own accord. That matches what the current silicon cells are performing at. This jump has spurred scientists and researchers to speculate what the limit of this new crystalline structure could accomplish. The most significant impact of this jump is that it has increased the number of researchers and developers looking at this method of solar energy, furthering the chances that it will surpass the expectations on it right now. Some have even suggested that a layer of perovskite with silicon could lead to an un-imagined 44% efficiency as early as 2017. Even a double-stack, layering perovskite on top of each other could increase the efficiency to 30%, without the need to combine it with other materials already in existence.
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Stanford and Oxford have created novel solar cells from crystalline perovskite that could outperform existing silicon cells on the market today. This design converts sunlight to electricity at efficiencies of 20 percent, similar to current technology but at much lower cost.
An efficient solar cell is the goal, but it can’t be feasible unless it’s going to compete on the energy market. This, alone, is the single most important goal of researchers looking at perovskite solar cells for their energy needs. Otherwise the ease and efficiency of the solar cell won’t mean much because no one will implement it into their solar energy designs.
As it happens, the production of the traditional silicon cells requires a pure silicon layer, 99.999% pure in fact. This level of purity comes at a steep price tag because of the production of the silicon. Even so, the cost of production has continually been cut down in recent years, but the price of a solar power system consists of traditional silicon cells is still high for an average family. Also the production requires much development and the release of harmful gases into the atmosphere to produce these photovoltaic cells. This limits the efficiency of the silicon in terms of cost-effectiveness.
Perovskite structured cells can really take the lead here. They are naturally forming crystalline structures, able to be harvested naturally without the need for production or laboratory design. This drastically reduces the costs to create an already efficient solar cell.
Watch this video also: Perovskite solar cells made simply by C&EN
As shown in this footage, ordinary lab equipment is all that’s required to make perovskite solar cells.
The other concern in manufacturing commercial solar cells is the stability. When talking about stability, it’s in two areas that matter most to producers of solar energy solutions. The cell structure must be stable and durable enough to withstand outdoor conditions. The production must also be stable, capable of being produced affordability and sustainably to meet the global energy crisis.
The problem is that the National Renewable Energy Laboratory, or the NREL, has a schedule of the efficiency of the current models of solar cells. The most advanced cell structure sits at 44%. That might seem exciting but that cell is neither stable in its production nor capable of competing on the market today. 44% is still, in every practical sense, unattainable by our current methods of harvesting solar energy.
Typically, solar cells made of silicon can last 25 years or more, which has been clearly recognized by many industry experts. But for a perovskite solar cell, as yet, there′s still no definite saying of how long it can last.
When it was first introduced, the original perovskite cell could only remain stable for a matter of minutes. As more developers, researchers, and universities saw the potential this structure represented, they too joined in the examination of the crystal. And as more people test and study the materials, more methods of stability are being produced almost weekly.
New methods, as new as just a few months ago, have been introduced to retain its stability in production and feasibility. A research team in Stanford has utilized tandem technology and subjected their experimental cells made with tin to temperatures of 212℉ (100℃) for 4 days, and found that the cells exhibited excellent thermal and atmospheric stability. (the research paper can be found here) “The efficiency of our tandem device is already far in excess of the best tandem solar cells made with other low-cost semiconductors, such as organic small molecules and microcrystalline silicon,” said the study co-author Michael McGehee. “Those who see the potential realize that these results are amazing.” Another co-author Henry Snaith also said that their next step is to optimize the composition of the materials to better absorb light and generate higher current. In short, the stability of perovskite solar cells has gained decent progress in the past year. But, including the Stanford team, researchers in this field are on the road to seeking more advanced method to better improve the stability.
Expectation for the Future
The same aspect of perovskite solar cells that make it exciting also make it, as of yet, unusable for commercial abilities. It’s just so incredibly new. There are a handful of companies that have developed a product that could go to market in 2017. Other experts claim that a functioning perovskite solar cell won’t be seen for another 5 years. Its development has been fast and exciting, but there is still a long way to maturity for this structure.
In a world that has remained stagnant for around 15 years, this jump in material has been a rejuvenating leap in the promise of a renewable energy source that is both cost-effective and mass marketable. Although many other photovoltaic cells have seen advancements in their technology, there still remains a material that has such promise as perovskite.