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A Chinese research group has designed a perovskite solar cell with a new ligand known as 3-amidinopyridine. Apparently, these molecules are capable of effectively reducing anion vacancy defects, thus ensuring higher energy conversion efficiency and remarkable stability.
Researchers at Shaanxi Normal University (China) have devised a novel control strategy to reduce the formation of anion vacancy defects in perovskite halide solar cells and found that this new approach results in higher efficiency and remarkable stability. .
The new method, which they define as a two birds with one stone strategy, uses a ligand known as 3-amidinopyridine (3AP) to bind the anions to the device. Anions can control the nucleation and growth of perovskite crystals and act as a passivating agent to improve crystallinity, thus ensuring higher efficiency.
Scientists claim that 3AP molecules deposited in the perovskite layer are capable of forming strong chemical bonds with the lead(II) iodide (Pb-I) interlayer of the cell and, as a consequence, creating a fixation effect. sustainable.
“We found that the 3AP molecules were arranged in parallel and antisymmetrically between the Pb-I structures with a short interlayer distance of 3.45 angstrom (Å), which is much shorter than that obtained for ligands from which previously reported, leading to unique coordination within crystals," they explained.
The researchers built the cell with a tin oxide (FTO) substrate, a titanium oxide (TiO2) electron transport layer, a halide perovskite called a-formamidinium lead iodide known as a-FAPbI3, a spiro-OMeTAD hole transport and a gold (Au) metallic contact.
They evaluated the performance of the device using density functional theory (DFT) calculations and compared it to that of a reference cell using commonly used large organic ligands such as 2-phenethylammonium (PEA) and n-butylammonium ( BA).
The group found that the 3AP-based cell achieved a maximum power conversion efficiency of 25.3%, an open circuit voltage of 1.181 V, a short circuit current of 26.04 mA cm-2, and a fill factor of 82.21%. The reference cell without 3AP molecules achieved an efficiency of 22.76%, an open circuit voltage of 1.123 V, a short circuit current of 24.94 mA cm-2 and a fill factor of 81%.
Through additional measurements, the academics also found that an unencapsulated 3AP-based cell was able to retain 92% of its initial efficiency after 5,000 h of exposure under ambient conditions. “Engineering anion-vacancy defects through strong molecule-perovskite coordination provides an effective and simple solution to increase both the efficiency and stability of perovskite solar cells,” they stated.
They presented the new anion gap control strategy in the study “ One-stone-for-two-birds strategy to attain beyond 25% perovskite solar cells ”. , published in nature communications. “Our findings offer an effective chemical strategy for the simple fabrication of stable, high-performance perovskite solar cells and are potentially applicable to other perovskite optoelectronic devices,” they concluded. |
