Developed by an international team including Saudi Arabia’s KAUST and the Chinese Academy of Science, the solar cell is claimed to be one of the most efficient perovskite PV devices based on 3D/2D heterostructures built to date.
An international research team led by the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia has developed a 3D/2D perovskite solar cell based on a meta-amidinopyridine (MAP) ligand that can reportedly improve ferroelectric properties and passivation effects at the cell’s 3D/2D interface without deteriorating charge transport.
Perovskite cells built with 2D hybrid materials are known for their stability and exhibit large exciton binding energy compared to conventional 3D devices. Different organic ammonium salts have been tested to develop 3D/2D solar cells, with halogenated analogs of phenethylammonium iodide (PEAI) salts being the preferred choice due to their potential to enhance hole extraction.
The researchers explained that currently 3D/2D perovskite heterostructures are formed by dissolving suitable ligands in polar solvents, which affects charge transport and cell stability. To address this issue, they used MAP ligands and the solvent post-dripping, which resulted in a “highly ordered” 2D perovskite phase on the surface of a 3D perovskite film, without significantly compromising the quality of the whole 3D/2D-MAP film.
“2D-MAP without post-dripping treatment exhibits a disordered orientation of the 2D phase atop the 3D perovskite,” they further explained. “In contrast, after solvent post-dripping, the 2D-MAP sample shows a more ordered 2D phase parallel to the 3D perovskite layer with a more infiltrated structure.”
The research team built the solar cell with a substrate made of glass and indium tin oxide (ITO), a hole transport layer (HTL) based on 2PACz, a 3D perovskite absorber, a 2D perovskite layer, an electron transport layer (ETL) based on buckminsterfullerene (C60), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
“The ordered 3D/2D-MAP-based devices show the largest potential drops and electric field enhancement at the perovskite/C60 contact, benefiting from the enhanced ferroelectricity of the ordered 2D-MAP layer,” the scientists stressed. “In addition, the electric field ratio between the perovskite/C60 and ITO/SAMs/perovskite interfaces increased.”
Tested under standard illumination conditions, the solar cell achieved a maximum power conversion efficiency of 26.05%, a certified efficiency of 25.44%, and a fill factor of 85.5%. For comparison, a benchmark solar cell without the 2D-MAP achieved an efficiency of 23.5 and a fill factor of 81.45%.
“Under damp heat and outdoor tests, the encapsulated perovskite solar cells maintain 82% and 75% of their initial efficiency after 1,000 h and 840 h, respectively, demonstrating improved practical durability,” the researchers said. “These results confirm the compatibility of our method with scalable deposition processes.”
The design of the solar cell was presented in the study “Solvent-dripping modulated 3D/2D heterostructures for high-performance perovskite solar cells,” published in nature communications. The research group included academics from the Chinese University of Hong Kong, Shaanxi Normal University, the Chinese Academy of Sciences, Korea University, and the National Technical University of Athens in Greece.