| Work Detail |
Chinese researchers have integrated a wide-bandgap perovskite solar cell with a hybrid back-contact device into a four-terminal tandem cell that achieves high efficiency and stability. The key to this high performance was a novel surface passivation strategy that the research group adopted for the top cell.
Researchers at Huaqiao University in China have fabricated a four-terminal (4T) perovskite-silicon solar cell with a superior cell based on a perovskite material with an energy bandgap of 1.67 and fewer surface defects.
The scientists used a surface reconstruction method to remove surface defects from the wide band gap perovskite by wet nanopolishing. “We found that the surface reconstruction strategy can improve the perovskite/C60 interface contact, release the residual lattice strain of the perovskite film, and form a bromine-rich perovskite surface layer, which effectively suppresses carrier loss at the interface and ion migration,” they explained,
The proposed technique was apparently able to remove defect-rich regions caused by improper crystallization on the surface of the perovskite film, as well as soft iodine-rich halide components that can fine-tune the energy level matching. Nanopolishing was found to re-tune the phase separation and suppress the inhomogeneity of the films crystallinity, which, according to the scholars, reduces the lattice mismatch between the surface and the bulk.
They also found that nanopolishing enhances the photoluminescence (PL) intensity of the perovskite film, ensuring a more uniform distribution of PL. “The measurements indicated a remarkable reduction of nonradiative carrier recombination in the perovskite films,” they added.
In the study, “ Surface reconstruction of wide-bandgap perovskites enables efficient perovskite/silicon tandem solar cells,” published in Nature Communications , the research group explains that it built the 300 mm × 300 mm perovskite cell using a glass and indium tin oxide (ITO) substrate, a hole transport layer (HTL) of nickel(II) oxide (NiOx) and a phosphonic acid called methyl substituted carbazole (Me-4PACz), and a perovskite absorber.
The researchers fabricated two different versions of this cell, one opaque and one semi-transparent, which achieved energy conversion efficiencies of 23.67% and 21.70%, respectively. In addition, both devices were found to retain 80% of their initial efficiency after operating at maximum power under sunlight for 1,505 h.
The team used the semitransparent cell to construct a tandem cell integrating a 158.75 mm × 158.75 mm back-contact (BC) silicon solar cell purchased from Gold Stone (Fujian) Energy Company Limited with an efficiency of 12.7% as the bottom device, and the large-area perovskite cell was placed on top of the BC silicon hybrid solar cell as a filter.
Tested under standard lighting conditions, the tandem cell achieved a power conversion efficiency of 33.10%.
“This work reveals that surface passivation of perovskite films with a high defect density, such as wide band gap perovskite films, requires a prior step to reduce the defect density in the initial films, indicating directions for the design of surface engineering strategies to further increase the performance of wide band gap perovskite solar cells,” the scientists stated. |
