| Work Detail |
Researchers have developed a novel passivation process for formamidinium-lead iodide perovskite films that reportedly resulted in solar cells with a power conversion efficiency of 23.69% and modules with a certified efficiency of 21.44%. After 1,000 hours, the heteropolymer-passivated devices maintained 92% of their initial efficiency, outperforming untreated ones.
An international research team led by South Korea’s Gwangju Institute of Science and Technology (GIST) has developed a passivation process for formamidinium lead iodide perovskite (FAPbI3) films, which it has demonstrated in solar cells with a certified power conversion efficiency of 23.69%, and in modules with a certified efficiency of 21.44%.
In terms of stability, heteropolyply devices passivated with an additional low-dimensional perovskite (LDP) layer maintained 92% of their initial efficiency after 1000 h, compared to 63% for an untreated reference device. And 6H-type perovskite devices without the LDP maintained 81%.
Their work is described in “ Shallow-level defect passivation by 6H perovskite polytype for highly efficient and stable perovskite solar cells,” published by Nature Communications .
“Until now, a typical approach has been to introduce an external chemical reagent to deal with the defect problem. However, introducing external reagents could directly affect the crystalline quality of the perovskite during crystal growth, so our work does not rely on such stabilizers,” said corresponding author Hobeom Kim of the Gwangju Institute of Science and Technology (GIST) in South Korea in a statement. “Instead, we employed a chemically identical perovskite polytype, the polytypic hexagonal perovskite (6H) that contains a shared corner component that effectively suppresses the formation of perovskite defects.”
To create the component, the team used excess lead iodide and methylammonium chloride to intervene with the dominant defect site. Specifically, they inserted 6H into the cubic (3C) polytype of the polycrystalline in FAPbI3. The process apparently improved the structural integrity and carrier dynamics of FAPbI3, resulting in an “ultra-long” carrier lifetime of over 18 microseconds.
Defect passivation consisted of depositing a surface passivation layer of octyl ammonium iodide on the 3 C/6H heteropolypic perovskite film to induce the formation of a low-dimensional perovskite (LDP) passivation layer.
The fabricated cells had a nip structure. They had a fluorine-doped tin oxide substrate, a titanium dioxide electron transport layer, a mesoporous titanium dioxide/potassium chloride layer, a perovskite absorber, a spiro-OMeTAD hole transport layer, and a gold metal contact.
The control device had an efficiency of 20.32%, while the 6H-bridged heteropolycrystalline polycrystalline film resulted in a device with an efficiency of 22.35%. Further efficiency improvement was achieved by an LDP passivation layer on the 6H-bridged perovskite film, resulting in a cell with an efficiency of 24.13%, an open-circuit voltage of 1.156 V, a short-circuit current density of 25.58 mA cm-2, and a fill factor of 81.60%.
The best cell certified by the Korean Energy Research Institute had an efficiency of 23.69%.
The team also fabricated 6.5 cm × 7.0 cm modules in a low-temperature process using eight passivated 3 C/6H heteropolypic perovskite LDP cells with P1, P2, and P3 interconnects. The best-performing module was certified by the Newport Photovoltaic Test and Calibration Laboratory with an efficiency of 21.44%.
In addition to the GIST team in South Korea, the study involved researchers from the Korea Basic Science Institute (KBSI) and the Korea Research Institute of Chemical Technology (KRICT), along with Toin University in Yokohama (Japan), Lomonosov Moscow State University (Russia), the École Polytechnique Fédérale de Lausanne (EPFL) (Switzerland), and King Abdulaziz University in Saudi Arabia. |
