Perovskite crystals are the big buzzword in solar power these days. Now, new research from a group of European universities finds that to maximize the amount of light that the crystals can convert into electricity, they’ll have to operate at incredibly fast speeds—femtoseconds, quadrillionths of a second. If they can, they could even surpass an efficiency rate of converting 30 percent of the sun’s light into electricity.
"We are talking about doing this extremely quickly, but it's not impossible that it could happen. Perovskite cells are very thin and this gives us hope, because the distance that the electrons have to cover is therefore very short,” said Johannes Richter, a PhD student at St John's College, Cambridge, UK, in the Cavendish Laboratory’s Optoelectronics group and the paper's lead author of the study, “Ultrafast carrier thermalization in lead iodide perovskite probed with two-dimensional electronic spectroscopy” published in the journal Nature Communications. Researchers from Cavendish and the Italian Politecnico di Milano, contributed to the report.
"Imagine if you had a pool table and each ball was moving at the same speed," Richter explained. "After a certain amount of time, they are going to hit each other, which causes them to slow down and change direction. We wanted to know how long we have to extract the electrons before this happens."
The researchers explained that moving electrons at femtoseconds would create "hot carrier” cells. Solar cells that can also harvest the kinetic energy that electrons have in the brief moment after they are created, while moving at the high speed.
"The timescale that we calculated is now the time limit that we have to operate within if we want to create super-efficient, hot carrier solar devices. We would need to get electrons out before this tiny amount of time elapses,” Johannes said.
Perovskite crystals have already demonstrated in lab tests efficiency levels as high as many silicon cells in the market. Last year for instance, researchers at Stanford and Oxford Universities produced a dual-layer, perovskite crystal-based solar cell that’s 20.3 percent efficient in laboratory testing.
The new devices could push perovskites even closer to the Shockley–Queisser limit, which is the proposed limit of efficiency for a single-layer solar cell, since it uses the energy in a different way. In fact, the authors say that perovskites could push the efficiency barrier further.
That would help increase interest in pushing perovskites from out of the lab and into the commercial sector. The technology promises lower costs than silicon because it needs much less material to be produced and could be produced with simpler manufacturing methods.Tweet