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All-perovskite tandem solar cell with 28.5% efficiency
A Chinese research team has fabricated an all-perovskite solar cell
with a 3D/3D double-layer
perovskite heterostructure that reportedly ensures improved charge
extraction.
The device achieved an open-circuit voltage of 2.112 V, a
short-circuit current of 6.5 mA cm-2, and a remarkable fill factor of
81.9%.
June 12,
2023
By
EMILIANO BELLINI
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The all-perovskite tandem solar cell
Image: Nanjing University
Researchers at the Nanjing
University in China have fabricated an all-perovskite tandem solar
cell that reportedly shows lower interfacial non-radiative
recombination and improved charge extraction.
All-perovskite tandem cells – where two different perovskite cells are
stacked on top of each other – promise efficiencies similar to those
of tandem
perovskite-silicon devices, well past the 30% mark, with better
flexibility, much lighter weight, and a lower environmental impact
than technologies relying on silicon wafers.
“All-perovskite tandem solar cells constructed by wide/narrow bandgap
perovskite cells have the advantages of high efficiency and low cost,
which is an important development direction of the next generation
photovoltaic technology,” the research team's lead author, Hairen Tan,
told pv
magazine. “Our all-perovskite tandem solar cells can be used
in power station power generation, rooftop photovoltaic, water
catalytic decomposition, carbon dioxide catalytic decomposition, and
space applications due to their high open circuit voltage and high
efficiency.”
The scientists also explained that in previously built all-perovskite
tandem devices perovskite suffered from low open-circuit voltage and
fill factor due to the high defect density on the surface of the mixed
narrow bandgap perovskite films based on lead and tin (Pb-Sn), which
causes cause serious non-radiation recombination loss at the interface
between the perovskite absorber and the buckminsterfullerene (C60)
electron transport layer (ETL).
“It is a common strategy to reduce the interface recombination loss of
perovskite cells by depositing a two-dimension (2D) perovskite layer
on the perovskite surface through solution post-treatment to form
2D/3D heterojunction structure,” Tan said. “However, the 2D perovskite
obtained by solution post-treatment has poor uniformity (layer n value
is difficult to control) and low conductivity, which is not conducive
to the interface transport and extraction of carriers.”
To solve these challenges, Tan's team designed a novel 3D/3D
double-layer perovskite heterostructure. Using a mixture of vacuum
evaporation and solution processing, a 3D pure lead wide-bandgap
perovskite film was grown on a Pb-Sn mixed narrow bandgap perovskite
film.
“The 3D pure lead wide-bandgap perovskite forms a Type-II
heterojunction structure with narrow bandgap perovskite, which
promotes the withdrawal of charge carriers from the perovskite
absorption layer to the electron transport layer, reduces the
interface recombination loss between perovskite/C60, and significantly
improves the open circuit voltage, fill factor and efficiency of the
solar cells,” Tan explained.
The solar cell achieved a power conversion efficiency of 28.5%,
an open-circuit voltage of 2.112 V, a
short-circuit current of 6.5 mA cm-2, and a fill factor of 81.9%, with
the Japan Electrical Safety and Environment Technology Laboratories
certifying a stabilized efficiency of 28.0%. “The encapsulated tandem
devices retain over 90% of their initial performance after 600 hours
of continuous operation under simulated one-sun illumination,” the
researchers stated.
The Chinese team also fabricated a cell with a large area of 1.05
cm2, and
its efficiency reached 26.9%.
The academics described the device in the study “All-perovskite
tandem solar cells with 3D/3D bilayer perovskite heterojunction,”
published in Nature. Looking
forward, they said some electrical
and optical losses should be further investigated to leverage the full potential of all-perovskite tandem solar cells.
“Potential methods to address the optical loss include reducing
optical reflection via light management, using more transparent front
electrodes and hole transport material, and exploring thicker narrow-bandgap
perovskite absorber layers,” they concluded.
Other researchers at the Nanjing University recently developed an all-perovskite
tandem solar cell with an efficiency of 24.2%.
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