While perovskites and carbon nanotubes are both hot topics for research, few studies have looked at combinations of the two. Research to date has established, while pure carbon nanotubes can boost the efficiency of perovskites when used as an electrode layer, the two do not bond well, leading to potential problems at the interface between layers.
Scientists at the Tokyo Institute of Technology chose to study that bonding mechanism in depth and found adding an oxygen-containing functional group to the nanotube structure strengthened interaction between the two layers, resulting in a better interface.
The team also found perovskite cells underwent a crystallization process when stored in the dark, further improving the interface. “We have discovered the self-recrystallization ability of perovskite at room temperature, whose morphology greatly improved after long-term storage,” said Keiko Waki, who led the research group. “However, the most interesting result was the ability of functionalized CNTs [carbon nanotubes] to make use of the self-recrystallization nature to form a stronger junction between the perovskite and CNTs through the reconstruction.”
The results, published in RRL Solar, showed cells with initial efficiencies of 3.21-7.89% improved to 9.54-12.14% after two months stored in an ambient medium with relative humidity of 20-50%.
While those efficiencies are far below what has already been achieved with similar perovskite materials, the researchers noted using carbon nanotubes could solve many of the stability issues associated with perovskites as the CNTs served to protect against moisture damage and also drove production of perovskites with fewer defects.
“We hope this study contributes toward the production of perovskites with higher stability and reproducibility,” added Waki.