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An international research group has created a triple junction perovskite solar cell with an efficiency of 24.3% and a quasi-steady-state efficiency of 23.3%.
Scientists from Canada, the United States and the United Kingdom have created a triple junction perovskite solar cell with a record efficiency of 24.3% and an open circuit voltage of 3.21 V. Their findings are collected in the article “ Suppressed phase segregation for triple-junction perovskite solar cells,” recently published in Nature.
The NREL has certified the cells quasi-steady-state efficiency to be 23.3%.
“To the best of our knowledge, this is the first certified efficiency of perovskite-based triple junction solar cells,” say the researchers, adding that perovskite triple junction solar cells have so far demonstrated a maximum efficiency of around 20%. .
The team started by using the ABX3 perovskite, which is made of a mixture of different substances, including cesium, lead, tin, iodine, bromine, and small organic molecules. Its upper layer is composed of mixed-halide perovskites with an especially high proportion of bromine (Br) and iodine (I).
“What happens in the light-induced phase separation of these mixed perovskites is that high-frequency photon bombardment causes the more bromine-rich phases to separate from the iodine-rich ones,” explains Dr. Hao Chen, study co-lead author. “This causes an increase in defects and a decrease in overall performance.”
To overcome this challenge, the academics used solid-state magnetic resonance spectroscopy to simulate the effect of altering the composition of the crystals. They found that replacing organic molecules with a fully organic perovskite structure and replacing cesium (Cs) with the element rubidium (Rb) suppressed light-induced phase separation (LIPS).
“We found that Rb, with a smaller cationic radius than Cs, can be doped in the inorganic perovskite lattice and that the upper limit of Rb doping content is positively correlated with Br content,” the scientists explain. “Rb/Cs mixed cation inorganic perovskites around 2.0 eV [bandgap] with a higher degree of lattice distortion than their Cs-based counterparts show suppressed LIPS due to decreased mean interatomic distance of the cation [Cs or Rb]-site and the I, and to the increase of the energetic barrier of the migration of halide ions”.
The triple junction cells retained 80% of their initial efficiency after 420 hours of operation at full power point.
The team is made up of researchers from the University of Toronto (Canada) and Northwestern University (United States). |
