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Chinese scientists have for the first time built a four-terminal tandem perovskite cell with an upper perovskite device with an efficiency of 17.88% and a lower antimony selenide cell with an efficiency of 7.85%. Key features of the tandem cell are the transparent conductive electrode used to enhance the spectral response of the upper cell and the “double” electron transport layer of the antimony selenide cell.
A group of researchers from the University of Science and Technology of China has fabricated a four-terminal (4T) tandem solar cell based on an upper cell that relies on a perovskite absorber and a lower device that uses an antimony selenide absorber. .
“Antimony selenide is a suitable material for tandem solar cells. “However, due to the paucity of reports on tandem solar cells using it as a bottom cell, little attention has been paid to its application.”
Antimony selenide (Sb2Se3) is a p-type inorganic semiconductor with a one-dimensional crystal structure and a direct bandgap in the range of 1.2 eV to 1.9 eV. It has excellent optoelectronic properties. In recent years, it has also been used as an absorbent material to build solar cells. The efficiencies achieved by such devices have reached between 5% and 9.2%.
These efficiency levels remain far behind those of other thin film technologies, such as cells based on copper, indium, gallium and selenide (CISG), cadmium telluride (CdTe), kesterite (CZTSSe) and amorphous silicon (a -Yeah). This technological gap could be due to the fact that the scientific community is largely unaware of characteristics such as mobility, carrier lifetime, diffusion length, defect depth, defect density and the band tail of the technology. of Sb2Se3 cells, since to date not many devices of this type have been manufactured.
The Chinese group presented its tandem cell in the study “ Sb 2 Se 3 as a bottom cell material for efficient perovskite/Sb 2 Se 3 tandem solar cells ” ), published in Energy Materials and Devices , and stated that the key features of the device are the transparent conductive electrode they used to improve the spectral response of the upper cell and the “double” electron transport layer (ETL) of the upper cell. antimony selenide.
The researchers designed the top cell with an f-doped tin dioxide (FTO) substrate, a tin oxide (SnO2) ETL, a perovskite absorber, a Spiro-OMeTAD hole transport layer (HTL), a molybdenum trioxide (MoO3) buffer layer and a transparent indium zinc oxide (IZO) contact.
The bottom cell was designed with a substrate made of FTO, an ETL made of tin(IV) oxide (SnO2) and cadmium sulfide (Cds), the absorber Sb2Se3, an HTL based on Spiro-OMeTAD, and a metal contact of gold (Au).
“We have successfully fabricated 4-T perovskite/Sb2Se3 tandem solar cells,” the scientists say. “IZO films prepared by magnetron sputtering generate both good conductivity and extraordinary transparency.”
Tested under standard lighting conditions, the upper cell achieved an efficiency of 17.88% and the lower one 7.85%. “Ultimately, the power conversion efficiency of the 4-T perovskite/Sb2Se3 tandem solar cells reached 20.58%, higher than that of the independent subcells,” the scientists stressed.
“Our work provides a new tandem device structure and demonstrates that antimony selenide is a promising absorbent material for background applications in tandem solar cells,” concluded the lead author of the research, Tao Chen. |
