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Developed by Chinese researchers, the inverted perovskite device reportedly achieves the lowest nonradiative recombination-induced open-circuit voltage loss recorded to date. It uses a synergistic bimolecular interlayer to functionalize the perovskite interface.
A group of scientists led by Chinas Fudan University has developed an inverted perovskite solar cell that uses a synergistic bimolecular interlayer (SBI) and reportedly achieves the lowest non-radiative recombination-induced open-circuit voltage loss ever recorded.
Inverted perovskite cells have a device structure known as a “pin,” in which the p-hole selective contact is at 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 researchers SBI strategy consisted of depositing 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI) as modulators to functionalize the perovskite surface.
“MPA induces an in situ chemical reaction on the perovskite surface by forming strong PO-Pb covalent bonds that decrease the surface defect density and raise the surface Fermi level,” they explain. “PEAI also creates an additional negative surface dipole so that a more n-type perovskite surface is built, which enhances electron extraction at the top interface.”
They also stressed that the proposed strategy does not affect the perovskites surface morphology, crystallinity or optical absorption properties, while contributing to a more effective passivation of defects.
The scientists built the cell with a fluorine-doped tin oxide (FTO) substrate, a hole transport layer (HTL) of phosphonic acid called methyl-substituted carbazole (Me-4PACz), a perovskite absorber, the SBI layer, a buckminsterfullerene (C60) electron transport layer (ETL) based on phenyl-C61-butyric acid methyl ester (PCBM), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
Using ultraviolet photoelectron spectroscopy (UPS), the team also found that the perovskite surface can fix the negative polaron transport state of the PCBM ETL, thereby further promoting electron transfer across the perovskite/ETL interface.
“In addition, the SBI-modified perovskite film exhibits a smaller surface potential distribution difference and lower surface roughness,” the team says. “A smoother perovskite surface with a more uniform surface potential distribution is beneficial for forming an efficient contact with the adjacent ETL that prevents nonradiative recombination.”
Tested under standard lighting conditions, the solar cell achieved an efficiency of up to 25.53% and a short-circuit current density of 24.31 mA cm2. It also achieved one of the lowest non-radiative recombination-induced open-circuit voltage losses of “only 59 mV” and a certified efficiency of 25.05%. “Furthermore, the target device also exhibits good stability, retaining 95% of its initial efficiency during an aging of more than 1000 h,” the academics added.
They described the new cell concept in the study, “ Reducing nonradiative recombination for highly efficient inverted perovskite solar cells via a synergistic bimolecular interface ,” recently published in Nature Communications . “These results demonstrate the important role of our SBI strategy on the surface properties of perovskite, which show great effectiveness in minimizing the trap density and constructing a perovskite surface with beneficial energetics, and pave the way for further improvements in perovskite solar cells,” the scientists concluded. |
