For years, perovskites have been hailed as the "holy grail" of solar energy thanks to their promise of highly efficient and cheaper solar cells. Perovskites are a class of materials with similar crystalline structures with high superconductivity, high magnetoresistance, and high ferroelectricity, making them a potential replacement for silicon. Perovskite thin-film PV panels can absorb light from a wider variety of wave-lengths, allowing them to reach efficiencies of around 40% compared to silicon's theoretical limits around 30%. Unfortunately, perovskites are notoriously unstable and highly susceptible to degradation when exposed to common environmental factors.
But now researchers at the University of Cambridge have unveiled a new halide perovskite that’s much more stable than conventional perovskites by fine-tuning them at the atomic level, opening the door for more powerful, durable and efficient devices.
The researchers used a vapour-based technique to create two- and three-dimensional perovskites one layer at a time, enabling them to accurately determine the thicknesses of the perovskite films down to fractions of an atom. Indeed, the scientists are able to create perovskite layers on the Angstrom level--or a tenth of a nanometer. They then meticulously stack these layers atop each other in a way that their atoms align perfectly, allowing their electrons and holes (the electrons’ positively charged opposites) to move freely in a process similar to the one used to make commercial semiconductors.
In effect, the layers act like one-way streets that guide charges and prevent them from wasting energy as heat. The researchers have achieved energy difference between the layers exceeding half an electron volt and extended the lifetime of electrons and holes to more than 10 microseconds, much longer than usual.
“Changing the composition and performance of perovskites at will – and probing these changes – is a real achievement and reflects the amount of time and investment we’ve made here at Cambridge,” said Professor Sam Stranks, who co-led the research. “But more importantly, it shows how we can make working semiconductors from perovskites, which could one day revolutionize how we make cheap electronics and solar cells.”
Perovskite technology has been advancing at a rapid pace. In 2012, scientists finally succeeded in manufacturing thin-film perovskite solar cells, which achieved efficiencies over 10%. But since then, efficiencies in new perovskite cell designs have skyrocketed: recent models can achieve 30%+, all from a thin-film cell that is (in theory) much easier and cheaper to manufacture than a thick-film silicon panel.
Last year, giant Chinese solar panel manufacturer Longi announced it has achieved a power conversion efficiency of 34.6% for a perovskite-silicon tandem solar cell, a new world record, beating the company’s previous record of 33.9% set in November 2023. The European Solar Test Installation (ESTI) certified the results .Longi is among the world's largest and leading solar manufacturers.
“We achieved this result by optimizing the thin film deposition process of the electron transport layer, developing and using high-efficiency defect passivation materials, and designing and developing high-quality interfacial passivation structures,” the company said in a statement, without providing further details.
Longi has broken the world record for solar cell efficiency more than a dozen times over the past four years. The company’s latest world beaters have actually surpassed the Shockley-Queisser (S-Q) theoretical efficiency limit of 33.7% for single junction solar cells.
Meanwhile, Qcells, a subsidiary of South Korea’s giant conglomerate Hanwha Corp, set a world record for the efficiency of a large-area silicon solar cell with a top layer of perovskite, a development that could dramatically shrink the size of projects and slash costs.
Qcells achieved a cell efficiency of 28.6% on a large commercial-sized cell known as an M10 using the technology, considerably higher than 27% efficiency for crystalline silicon cells and around 21% for traditional commercial silicon solar panels. Longi’s higher efficiency is for much smaller cells.
"If you have 100 solar panels in the field, but you can get the same power output for only 60 or 80 of them, now you're digging less holes, you're using less rails, you have less labor to install it," Danielle Merfeld, Qcells' chief technology officer, told Reuters.
Qcells’ discovery comes at a time when extensive land use by large solar projects is increasingly becoming a major challenge. For instance, California's Solar Star Project is among the largest solar energy facilities in the world, boasting 1.7 million panels spread over 3,000 acres north of Los Angeles. In comparison, a natural gas power plant located 100 miles south of Solar Star produces the same amount of energy on just 122 acres.
By Alex Kimani for Oilprice.com
