Researchers from Colorado University in Boulder with the US Department of Energy’s National Renewable Energy Laboratory (NREL) have shown how a change in chemical composition managed to boost the longevity and efficiency of a perovskite solar cell.
The new formula reportedly enabled the solar cell to resist a stability problem that has so far thwarted the commercialization of perovskites. The problem is known as light-induced phase-segregation, which occurs when the alloys that make up the solar cells break down under exposure to continuous light.
“Now that we have shown that we are immune to this short-term, reversible phase-segregation, the next step is to continue to develop stable contact layers and architectures to achieve long-term reliability goals, allowing modules to last in the field for 25 years or more,” said Caleb Boyd, lead author of study. Boyd and co-author Jixian Xu are associated with University of Colorado-Boulder Professor Michael McGehee’s research group, which investigates perovskites at NREL.
Perovskite solar cells are typically made using a combination of iodine and bromine, or bromine and chlorine, but the researchers improved upon the formula by including all three types of halides. The research showed the feasibility of alloying the three materials.
Adding chlorine to iodine and bromine created a triple-halide perovskite phase and suppressed the light-induced phase-segregation even at an illumination of 100 suns. What degradation occurred was slight, at less than 4% after 1,000 hours of operation at 60 degrees Celsius. At 85 degrees and after operating for 500 hours, the solar cell lost only about 3% of its initial efficiency.
“The next step is to further demonstrate accelerated stability testing to really prove what might happen in 10 or 20 years in the field,” Boyd said.
The new formula created a solar cell with an efficiency of 20.3%.