| Work Detail |
Researchers in China have fabricated a TOPCon tandem perovskite solar cell with a perovskite top layer using a self-assembled monolayer designed to improve cell stability. The tandem cell achieved a high fill factor and a certified efficiency of 30.9%. A group of researchers led by Zhejiang University in China has fabricated a perovskite-TOPCon tandem solar cell with an inverted perovskite top cell using a self-assembled monolayer (SAM) that can reportedly improve the cell’s thermal stability. Inverted perovskite cells have a device structure known as “pin,” in which the hole-selective contact p is on the bottom of the intrinsic perovskite layer i, with the electron transport layer n on top. Conventional halide perovskite cells have the same structure but inverted: a “nip” arrangement. In the nip architecture, the solar cell is illuminated through the electron transport layer (ETL) side; in the pin structure, it is illuminated through the hole transport layer (HTL) surface. The scientists explained that the electron density within SAMs can be modulated to shift the interfacial energetics between the SAM and the perovskite layer, resulting in a “more versatile and controlled approach” to optimizing energy alignment in the perovskite solar cell, while also having a “negligible” influence on the phase stability of the wide-bandgap perovskite film. The team built the perovskite top cell with an indium tin oxide (ITO) layer, the SAM, a nickel oxide (NiO) layer, a perovskite absorber with a 1.68 eV band gap, a lithium fluoride (LiF) layer, an electron transport layer (ETL) based on fullerene (C60) and tin oxide (SnO2), a transparent indium zinc oxide (IZO) back contact, and a silver (Ag) metal contact. Tested under standard lighting conditions, the top perovskite cell was found to have a power conversion efficiency of 22.8%, an open-circuit voltage of 1.24 V, and a “high” fill factor of 84.3%. It was also observed to maintain more than 99% of its initial efficiency after 400 h of maximum power point tracking at 60°C. Using this cell, the researchers built a 1 cm² tandem device that includes a standard TOPCon solar cell as the bottom device. This cell achieved a measured internal efficiency of 31.1% and a certified efficiency of 30.9%, with the results verified by the National Photovoltaic Product Quality Inspection and Testing Center of the Chengdu Product Quality Inspection Institute. It also achieved an open circuit voltage of 1.88 V, a short circuit current of 20.0 mA cm-2 and a “high” fill factor of 82.6%. The researchers stated that these figures demonstrate the reliability and application potential of the inductive modification strategy for wide-bandgap perovskite solar cells. “The results highlight the possibility of rationally designing SAMs by leveraging the inductive effect to achieve favorable interfacial energetics with wide-bandgap perovskites,” they emphasized. “We believe this strategy holds promise for contributing to the commercialization of perovskite and perovskite-TOPCon tandem solar cells.” The novel cell concept was presented in the article “ Inductive effects in molecular contacts enable wide-bandgap perovskite cells for efficient perovskite/TOPCon tandems,” recently published in Nature Communications . In July, other researchers at Zhejiang University in China announced they had developed the first inverted perovskite solar cell based on a high-entropy hybrid perovskite material that reportedly improves device stability while providing excellent efficiency levels. |
