Novel defect passivation strategy improves the efficiency and stability of perovskite solar cells
Solar energy remains a crucial component in reducing dependence on fossil fuels and transitioning to cleaner energy sources. Over time, solar cells have made significant progress, becoming increasingly efficient at harnessing renewable energy.
Metal halide perovskite has become an important material for solar cells due to its impressive optoelectronic properties, which allow it to effectively convert sunlight into energy.
One of the key materials for creating high energy conversion efficiency (PCE) in perovskite solar cells (PSCs) is polycrystalline formamidinium lead iodide (FAPbI3), known for its narrow energy bandgap. However, despite their excellent properties, polycrystalline perovskites such as FAPbI3 suffer from defects in their crystal structure. These imperfections affect their structural stability and their ability to convert energy, hindering their overall performance.
In response to this challenge, a research team led by Professor Hobeom Kim from Gwangju Institute of Science and Technology (GIST) has developed an innovative defect passivation strategy aimed at significantly reducing these defects and improving both efficiency as the stability of perovskite solar cells. Their study, published on July 4, 2024 in ‘Nature Communications’, introduced a hexagonal polytype (6H) perovskite into the cubic polytype (3C) FAPbI3. This development led to a significant improvement in PCE compared to other variants.
“A typical approach so far has been to introduce an external chemical reagent to address the defect problem. However, introducing external reagents could have a direct impact on the crystalline quality of the perovskite during crystal growth, so our work is not dependent of such stabilizers. Instead, we use a chemically identical polytype perovskite, the 6H polytype that contains a corner-sharing component that effectively suppresses the formation of defects in perovskite,” explains Prof. Kim.
The team integrated the 6H perovskite into FAPbI3 using excess lead iodide and methyl ammonium chloride. This process created a component that interacted with the primary defect site of the cubic polytype (3C) FAPbI3, improving its structural integrity and carrier dynamics. The result was ultra-long carrier lifetimes of over 18 microseconds and PSCs with a PCE of 24.13%. The module achieved a PCE of 21.92%, with a certified efficiency of 21.44%, along with long-term operational stability.
The researchers suggested that the combination of the 3C and 6H polytypes could be the optimal configuration for a polycrystalline perovskite film. This discovery paves the way for further advancements in PSC technology, making it more feasible for both personal and commercial applications, such as rooftop solar panels, wearable devices and portable chargers.
“Perovskite solar cells offer a transformative solution for achieving carbon neutrality and tackling global warming. Their efficiency, versatility and reduced environmental impact make them an essential component in the transition to a sustainable future,” concluded Prof .Kim.
Research report:Shallow defect passivation by 6H perovskite polytype for highly efficient and stable perovskite solar cells
