A Chinese research team has produced an all-perovskite solar cell with a 3D/3D double-layered perovskite heterostructure, which is said to ensure better charge removal. The device achieved a breakdown voltage of 2.112 V, a short-circuit current of 6.5 mA cm-2 and a remarkable duty cycle of 81.9%.
All-perovskite tandem cells – where two different perovskite cells are stacked on top of each other – promise similar efficiency to tandem perovskite-silicon devices, well above the 30% mark, better flexibility, much lighter and more environmentally friendly. more than technologies based on silicon wafers.
“All-perovskite tandem solar cells built from wide/narrow bandgap perovskite cells have high efficiency and low cost, which is an important development in next-generation photovoltaic technology,” said Hairen Tan, lead author of the research team. pv magazine. “Our all-perovskite tandem solar cells can be used in power plant power generation, rooftop solar, water catalytic decomposition, carbon dioxide catalytic decomposition, and space applications due to their high open-circuit voltage and high efficiency.”
The researchers also explained that in previously built all-perovskite tandem devices, the perovskite suffered from low open-circuit voltage and fill factor due to the high defect density on the surface of the lead- and tin-based (Pb-Sn) mixed narrow-band perovskite films. , which causes severe non-radiative recombination loss at the interface between the perovskite absorber and buckminsterfullerene (C60) electron transport layer (ETL).
“A common strategy is to reduce the interfacial recombination loss of perovskite cells by depositing a two-dimensional (2D) perovskite layer on the perovskite surface through solution post-treatment to form a 2D/3D heterojunction structure,” Tan said. “However, the 2D perovskite obtained by solution post-processing has poor uniformity (it is difficult to control the n-value of the layer) and low conductivity, which does not promote interfacial transport and carrier extraction.”
To address these challenges, Tan’s team designed a new 3D/3D bilayer perovskite heterostructure. Using a combination of vacuum evaporation and solution processing, a 3D pure lead wideband perovskite film was grown on a Pb-Sn doped narrowband perovskite film.
“The 3D pure lead wide-band perovskite forms a type II heterojunction structure with the narrow-band perovskite, which promotes the withdrawal of charge carriers from the perovskite absorption layer to the electron transport layer, reduces the interfacial recombination loss between perovskite/C60, and significantly improves the open-circuit voltage, fill factor and efficiency of solar cells,” explained Tan.
Solar cell achieved power conversion efficiency 28.5%, open circuit voltage 2.112 V, short circuit current 6.5mA cm-2, and a duty cycle of 81.9%, and Japan Electrical Safety and Environment Technology Laboratories certified a uniform efficiency of 28.0%. “The encapsulated tandem devices retain more than 90% of their original performance after 600 hours of continuous operation under simulated single-sun illumination,” the researchers concluded.
The Chinese team also produced a cell with a large surface area 1.05 cm2, and its efficiency was 26.9%.
The academics described the device in a study published in “All-perovskite tandem solar cell with 3D/3D two-layer perovskite heterojunction”. Nature. While waiting they said some electrical and optical losses should be investigated in more detail lforever the size potential / all perovskite tandem sun- cells. “Possible methods to correct optical loss include reducing optical reflection through light control, using more transparent front electrodes and hole transport material, and exploring thicker narrowband perovskite absorber layers,” they concluded.
Other researchers at Nanjing University recently developed a perovskite-only tandem solar cell with an efficiency of 24.2%.