Researchers from Australia's University of New South Wales (UNSW) explore challenges for perovskite solar cells under reverse-bias conditions, and propose strategies to address them in new study published in scientific journal Joule.
Famous solar researcher and inventor of PERC cell technology, Professor Martin Green, along with fellow Lead Investigator of the research, Dongchen Lan believe improved understanding of reverse-bias effects are important if perovskites are to become a commercial reality.
According to the researchers, any shading for perovskite cells such as by a fallen leaf, can lead to reverse-bias operation by cells with higher current output. Reverse-bias is when the applied voltage goes in the reverse direction, from high to low. For perovskites, the duo believe it will lead to more severe heating issues in this condition, which can be detrimental for flexible modules.
Green and Lan suggest various approaches to protecting thin film modules from reverse-bias. One of the approaches is to subdivide a long-thin cell module into series/parallel connection of smaller cells. This approach requires an extra laser scribing step, along with standard scribe process, and has recently been introduced by American manufacturer First Solar's Series 6 CdTe modules, after which these were shown to be susceptible to transient shadows.
Another approach the study recommends is to provide a bypass protection just as it there for silicon modules, but one for each perovskite cell in a module. They argue that this may be possible at low cost by integrating bypass diode into each cell. SunPower, that has now spun-off its manufacturing into Maxeon Solar Technologies, has used this technique, however it is not directly transferable to perovskites.
Perovskites are considered by many in the solar industry the next big thing in solar cell technology, in particular in combination with crystalline solar in tandem cells. However, while one efficiency record after another is being published for the technology in recent years, there's still some work to be done before this technology will be seen in mass production. Prof. Christoph Ballif from Switzerland's École Polytechnique Fédérale de Lausanne (EPFL) and Center for Electronics and Microtechnology (CSEM), who recently breached the 30% power conversion efficiency barrier for perovskite-on-silicon tandem solar cells, cautioned "Several years of R&D are still needed to bring such technology and manufacturing processes to market." Adding, "A big challenge will be developing solar cells that can remain stable on our rooftops for more than 25 years" (see Record Tandem Cell Efficiency Made in Switzerland).
Detailed research of UNSW titled Combatting Temperature and reverse-bias challenges facing perovskite solar cells is available on Joule's website.