Every year, the Czech Academy of Sciences gives out the Otto Wichterle Award. It goes to exceptional scientists under 35 who achieve top results at the very start of their careers. This year’s laureate from the Institute of Physics of the CAS is Aleš Vlk, who has been focusing on halide perovskites since 2018, materials with the potential to fundamentally improve the efficiency of harvesting energy from the sun.
Good news for solar energy
Silicon solar panels are today the most common renewable energy technology. However, they have their limits. For physics-related reasons, silicon alone can convert less than 30% of incident solar energy into electricity.
"The next step to increase efficiency is to add another solar cell on top of the silicon one, one that absorbs only the visible part of the solar spectrum,“ Aleš Vlk explains.
Of all known materials, halide perovskites are the only ones capable of serving as this top cell. Perovskite cells process higher-energy light more efficiently, which silicon would otherwise largely convert into heat. This creates a so-called tandem solar cell, bringing the potential to reach an efficiency of up to 45 %. In laboratories, such tandems already reach efficiencies of 35 %.
However, commercial use is still some way off. The stability of the perovskite layer remains the key issue. "Manufacturers offer a warranty of at least thirty years on silicon photovoltaics. Perovskites have made great progress in the last few years, but they still do not reach a thirty-year lifespan," Aleš Vlk says. No one knows exactly how these materials will behave in real conditions over the entire lifespan of the panel.
One promising branch of current research is the plasma treatment of the perovskite surface, which is being studied in collaboration with Masaryk University in Brno and EPFL in Neuchâtel (Switzerland). Surface defects and grain boundaries reduce solar cell efficiency, and plasma could help reduce their number. "The results are promising so far, but there is still a lot of work ahead," Aleš Vlk adds.
The path to the Otto Wichterle Award
This year, the Otto Wichterle Award goes to a scientist who explored various fields during his studies. He joined the Institute of Physics from the Faculty of Nuclear Sciences and Physical Engineering at the Czech Technical University (CTU) in Prague.
He spent his bachelor's studies there, majoring in Experimental Nuclear and Particle Physics. He then shifted to the study of laser welding of steels during his master's degree at the Department of Solid State Engineering. It was there, during lectures on superconductivity, that he met his future PhD supervisor, Martin Ledinský, who himself received the Otto Wichterle Award a few years ago.
He still remembers his first day in the lab at the Institute of Physics. His task was to measure the temperature dependence of photoluminescence in perovskite thin films. His supervisor sat him down at the instrument, handed him the manual, and left for three hours. "He told me he had to go to a lecture, so I shouldn't call him," Aleš Vlk recalls with a laugh. It was precisely this freedom and independence that appealed to him, and it remains one of the things he enjoys most about his work.
The award is named after Otto Wichterle, an outstanding Czech chemist of world renown, who became president of the Czechoslovak Academy of Sciences after November 1989. It has been given since 2002 and includes a financial reward of 330,000 Czech crowns, spread over three years.
Photo: Josef Landergott