A Chinese research team has designed a perovskite solar cell with a new ligand known as 3-amidinopyridine. These molecules are said to be able to effectively reduce anion vacancy defects, which ensures higher power conversion efficiency and remarkable stability.
The new method, which they described as a one-stone-two-birds strategy, used a ligand known as 3-amidinopyridine (3AP) to attach anions to the device. Anions can control the nucleation and growth of perovskite crystals and act as a passivating agent to improve crystallinity, ensuring better efficiency.
The researchers claim that the 3AP molecules deposited on the perovskite layer are able to form strong chemical bonds with the cell’s lead(II) iodide (Pb-I) interlayer, thus creating a durable anchoring effect.
“We found that the 3AP molecules were arranged parallel and antisymmetrically between the Pb-I frameworks with a short interlayer distance of 3.45 angstrom(Å), which is much shorter than that obtained with previously reported ligands, leading to unique coordination within the crystals, they explained.
The researchers built the cell on a substrate made of tin oxide (FTO), titanium oxide (TiO2) electron transport layer, halide perovskite known as α-formamidinium lead iodide known as α-FAPbI3, spiro-OMeTAD hole transport layer, and a gold (Au) metal contact.
They evaluated the performance of the device using density functional theory (DFT) calculations and compared it to a reference cell utilizing commonly used large organic ligands such as 2-phenethylammonium (PEA) and n-butylammonium (BA).
The team found that the 3AP-based cell achieved a maximum power conversion efficiency of 25.3%, an open-circuit voltage of 1.181 V, and a short-circuit current of 26.04 mA cm.−2and 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−2and a fill factor of 81%.
With further measurements, the researchers also verified that the 3AP-based cell without encapsulation was able to retain 92% of its original efficiency after 5000 hours of exposure under ambient conditions. “Anion-vacancy defect engineering through strong molecular-perovskite coordination provides an efficient and simple solution to increase both the efficiency and stability of perovskite solar cells,” they concluded.
They presented a new anion defect control strategy in a study published in “One stone for two birds strategy achieves more than 25% perovskite solar cells” nature communication. “Our findings provide an efficient chemical strategy for the facile fabrication of high-performance stable perovskite solar cells and may potentially be applied to other perovskite optoelectronic devices,” they concluded.