We may have it all wrong when it comes to organic and inorganic perovskites in solar cells. A new study has found fully inorganic halide perovskite materials have the potential to outperform those that are organic/inorganic hybrids.
The research, conducted by a team at the University of California, Santa Barbara, dispels the common impression that organic molecules (containing carbon and hydrogen) in perovskite material are more crucial to achieving the 25% (or more) photovoltaic efficiency touted for hybrid organic/inorganic perovskites. According to the study, “these critical insights may prevent all-inorganic halide perovskites from being disregarded as potentially strong candidates for solar cell materials.”
Xie Zhang, an assistant professor at UCSB and lead author of the study, says the team found that “when light shines on a solar cell material, the photo-generated carriers generate a current. Recombination at defects destroys some of those carriers and hence lowers the efficiency. Defects thus act as efficiency killers.” He notes that their work compared all-inorganic perovskites as well as hybrids in two prototype materials containing lead and iodine atoms. In one of the materials, the crystal structure was completed by cesium (an inorganic element); in the other, methylammonium (an organic molecule) was present. The research showed specifically defects that are common with both materials “give rise to comparable (and relatively benign) levels of recombination.” The organic molecule in the hybrid perovskite can break up when loss of hydrogen atoms occurs, the researchers say, with the resulting “vacancies” strongly decreasing efficiency. “The presence of the molecule is thus a detriment, rather than an asset, to the overall efficiency of the material.”
“We hope that our findings about the expected efficiency will stimulate more activities directed at producing inorganic perovskites,” says Chris Van de Walle, a materials professor at UCSB. Reference: X. Zhang, M. E. Turiansky, and C. G. Van de Walle, Cell Rep. Phys. Sci. (Oct. 11, 2021); doi:10.1016/j.xcrp.2021.100604.
