Intrinsic instability issues with organic-inorganic halide perovskites have been curbing the advancement of solar cells using such materials. And researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan have now found reasons to believe that scientists may not be able to overcome the degradation issue in methylammonium lead iodide (MAPbI3) perovskites, the most widely studied perovskites formulations used in solar cells.
Although solar cells made of MAPbI3 perovskites can reach efficiencies of 20% or more and are relatively inexpensive to fabricate, these devices have been presenting too short of a lifespan to become a commercially viable alternative to silicon solar cells.
How OIST concludes degradation in MAPbI3 perovskites may not be fixable
“It has been reported that to some extent the degradation of MAPbI3 showed similar behaviors in air and in vacuum, suggesting that the degradation of MAPbI3 is not always caused by ambient exposure or humidity,” says Professor Yabing Qi, head of the Energy Materials and Surface Sciences Unit at OIST and corresponding author of the research article “Accelerated degradation of methylammonium lead iodide perovskites induced by exposure to iodine vapour,” published in the journal Nature Energy. “Our work provides convincing evidence for the accelerated degradation of MAPbI3 when exposed to I2 vapor. Because I2 can be generated as a product from the initial degradation of MAPbI3, this presents a self-degradation pathway for MAPbI3 perovskite solar cells.”
Impact on future of perovskite solar cells
To better understand and potentially seek solutions to the instability problem with MAPbI3 perovskite solar cells, the OIST team has been investigating eventual causes for the rapid degradation. However, Qi points out: “Our findings indicate that it is very unlikely that encapsulation alone can solve the stability issue for MAPbI3 perovskite solar cells.”
Overcoming MAPbI3 degradation to design better generations of perovskite solar cells
“Our study suggests that to achieve long-term stability, it is necessary to develop other types of perovskite material in which mobile ions can be suppressed and I2-induced reactions can be mitigated,” Qi notes. Moving ahead with this research work, his team wants to develop methods to reduce such I2-induced degradation in perovskite solar cells, according to the professor.
Written by Sandra Henderson, Research Editor, Solar Novus Today