By now *everybody* knows that perovskite solar cells are the wave of the future. Unfortunately the future is on hold at present as all attention turns to the COVID-19 crisis. Nevertheless, there will be a future, and perovskite technology is poised to dominate the solar industry of the future — especially if researchers can manage to unravel the trap state trap, that is.
Wait, What Is The Perovskite Solar Cell Trap State Trap?
In a solar cell, trap state refers to defects. Understanding what those defects are and where they are located is a critical task for researchers who are racing to push the solar energy conversion limit for perovskite solar cells.
The latest news on that score comes from a newly published paper in the journal Science titled, “Resolving spatial and energetic distributions of trap states in metal halide perovskite solar cells.”
Got all that? Good — you win!
For the rest of us in the general reading public, the study abstract provides a bit more of a plain-language explanation. The researchers write that “the high efficiency of hybrid inorganic-organic perovskite solar cells is mainly limited by defects that trap the charge carriers and lead to unproductive recombination.”
Still lost? Fortunately, the corresponding author of the study, Professor Jinsong Huang of the University of North Carolina, is here to lend a hand. CleanTechnica spoke with Professor Huang last week and he shed some further light on the topic.
“Trap states play a critical role in the stability and efficiency of a solar cell,” he explained. To make things even a little more easy to grasp, he suggested conjuring up the image of a hole in a road to represent a trap state.
Depending on how shallow or deep the hole is, it could slow you down — or even trap you inside.
Now we’re getting somewhere.
Say you’re walking down the sidewalk and you come across a missing slab. You glide across the shallow depression with only a slight hitch in your pace.
All is well and good until a few yards farther along, when you suddenly step into a legit hole and perform a face plant.
Struggling back to your feet with a bloody nose, a chipped tooth, and a minor concussion, you turn from the sidewalk and wobble into the street. Good luck with that on coming traffic!
Onward & Upward For Perovskite Solar Cells
In a nutshell, that’s why it is important to understand the nature of trap states in a perovskite solar cell — and to understand where they are, too.
The new study represents important progress in that area. It indicates a pathway for anticipating solar cell efficiency that cuts out the time and expense of interim steps.
“It is difficult to measure the impact of trap states,” explained Huang. “Here, we have figured out a way to identify the location of the defects.”
“We have also found a way to measure how the defects are different, as in deep traps versus shallow traps,” he added. “Once you know the traps, you can predict how efficient the solar cell will be.”
How Low Can Solar Go?
He raised the prospect that cost-shifting could help keep bringing down the price of silicon solar cells over the years, though there isn’t much room to continue the steep declines of the past 10 years or so.
“The price of solar has dropped a lot with silicon, but it can only drop so much,” he said. “People are trying to squeeze costs down a little more, but there is really not much more you can do…with perovskite it’s totally different because you can do roll-to-roll manufacturing. It’s an unprecedented opportunity.”
Sounds good. It will sound even better when COVID-19 is under control.
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Photo (cropped): Professor Jinsong Huang (r.) with colleague, by permission of Professor Jinsong Huang, University of North Carolina — Chapel Hill.
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