Perovskites are expected to play a crucial role in the progress of solar energy worldwide. The market ripens quickly as breakthroughs of research and development continue to act.
As solar cells on silicon go on the basis of the scope and reach them to their theoretical limits, Perovskiet tandems have come forward to push the efficiency higher.
Perovskites are a material that can be used as the active material in solar cells itself and can be deposited in extremely thin layers, so that the door is opened at many different locations for applications. Nowadays, perovskites are mainly investigated as tandems, deposited as a layer on the above conventional silicon solar cells.
The more efficient a solar panel is, the more total system costs are sent and the more power you can get from a limited area as a residential roof.
Longi currently has the record for the efficiency of silicon solar cells and reaches just over 27%. It recently achieved 34.6% efficiency with a silicon-perovskiet tandem. Researchers from the Fraunhofer ISE model of Germany that tandems can achieve a practical efficiency of up to 39.5%, much further than what silicon can do in itself.
Perovskites tandems have applications for solar products and projects of all types of sizes, from mobile devices to solar projects on utility scale, but one of the most exciting direct applications can be for solar on the roof, said Ernest “Charlie” Hasselbrink, the Chief Technology Officer at Caelux.
“If you can add 30% [efficiency] In a residential panel, in a system that costs $ 3/W, add $ 0.90/w value that you can pick up for money, ”said Hasselbrink PV Magazine USA.
PV Magazine USA sat down for an interview with Hasselbrink, the CTO at Caelux, a specialist in four-terminal perovskiet-tandems to discuss Differences in two leading development paths.
2T or 4T
Two main architectures have currently been investigated by the industry today: a two-terminal (2T) and four-terminal (4T) approach. The 4T tandem structure has autonomous electrical connectivity with its two cells, while the 2T architecture is series-bonds.
While Longi’s record tandem was set with 2T architecture, which offers slightly higher boosts for efficiency, for various reasons, Hasselbrink sees better applications for 4t -dandems. Since perovskiet chemistry is still being investigated to increase reliability and long -term performance in the field, 4T can offer more flexibility in the available options for researchers.
Firstly, 4T perovskites can be placed on a completely separate substrate of the silicon solar cell, while 2T is not possible. This can be important because it gives perovskiet developers fewer restrictions for which substrate they use, which may lead to a more sustainable design. Sustainability of performance remains the Central problem to solve For perovskite use in the field.
“Our approach is, let’s cover this on the glass, and then there is almost no change for one of our customers, traditional manufacturers of silicon module,” said Hasselbrink. “They can build their panel like them
Moreover, 4T offers better flexibility for BandGap design. The tire gap is the minimum energy required to generate an electron in a semiconductor in a higher energy state. With 2t -dandems streams have to be matched, which means that once the band gap has chosen a cell, there is a limited flexibility for the band gap of the perovskiet cell. With 4T, the solution space is wider, which makes more flexibility possible for chemistry that are more stable.
Hasselbrink said that by being placed on their own substrate, 4T Perovskites benefit from chemical, mechanical and electrical insulation. 2T dandems are often deposited on the structured surface of the silicon cell, resulting in slightly better light absorption, but it can also cause limitations for perovskiet developers because they explore various chemical and mechanical configurations.
“Why limit the solution space for a small advantage?” Said Hasselbrink.
Another advantage for process and design flexibility is that 4T must be voltage instead of current coordinated, said Hasselbrink. More than about 10-15% current mismatch is a major challenge for sustainability, resulting in very hot cells if they are not well circumvented. 4T tandems, on the other hand, are tension-matched.
“The voltage of solar cells only depends weakly on the irradiation – even when the irradiation drops half, the voltage only drops by ~ 5%,” Hasselbrink said. “This is not enough to create large mismatch, performance losses or reliability problems.”
Scalability
Hasselbrink said that much of the protagonist reached by perovskites are made using non-economically feasible processes and often ignoring problems with the production fecton that can occur on a scale.
He said that Caelux is developing his laboratory processes with scalability in mind, with the help of equipment that is a smaller version or even manufactured by the same supplier as their production equipment. This approach streamlines the transition from research into production, he said.
Focus on sustainability
Hasselbrink warned that the research and development community may be too focused on efficiency gains, and more focus should be placed on sustainability and reliability, which remains the most important innovation factor for perovskites.
“The National Renewable Energy Laboratory Efficiency Chart offers academic teams the opportunity to get their name at the global stage by achieving the best efficiency,” said Hasselbrink. “There can be enormous value in creating similar graphs for sustainability: the best performance in composite outside tests, as well as in and in specific, standardized accelerated tests (which give much faster feedback).”
Labs that emphasize reliability in reporting can steer the research community in a more important direction, he said.
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