An international team of researchers from King Abdullah University of Science and Technology (KAUST), Ulsan National Institute of Science and Technology (UNIST) and the Chinese Academy of Sciences have reportedly developed an inverted perovskite solar cell incorporating low-dimensional perovskite layers at the solar cell's top and bottom interfaces.
The team achieved optimal passivation in inverted perovskite solar cells by applying thin layers of low-dimensional perovskite on top of a 3D perovskite film. The resulting cell achieved an open-circuit voltage of 1.19 V, a short-circuit current density of 24.94 mA cm2, and a fill factor of 85.9%.
In the 'inverted' p-i-n architecture, the solar cell is illuminated through the electron-transport layer (ETL) side; in the conventional n-i-p structure, it is illuminated through the hole‐transport layer (HTL) surface. The researchers explained that optimal passivation in perovskite solar cells is typically achieved by applying thin layers of low-dimensional perovskite on top of a 3D perovskite film, and said it is critical to have perfect control over the thickness, purity, and dimensionality of the low-dimensional layers on the top and bottom of 3D perovskites to minimize the energetic losses at these interfaces.
In their recent work, the team conducted extensive testing that helped it identify the ligand that exhibited the most effective interaction with the 3D perovskites for double-side passivation.
The scientists said that the proposed technique is aimed at minimizing the dissolution of 2D ligands during perovskite solution, in order to strengthen their interaction with the substrate, which they added allows for immobilizing 2D ligands before perovskite deposition.
They fabricated a cell with a substrate made of glass and indium tin oxide (ITO), a dimethoxy carbazole (Me-2PACz) layer, a 2D perovskite layer, a 3D perovskite absorber, a 2D perovskite layer, a buckminsterfullerene (C60) electron transport layer, a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
The team conducted a series of tests under standard illumination conditions and found the device achieved a power conversion efficiency of 25.63%, an open-circuit voltage of 1.19 V, a short-circuit current density of 24.94 mA cm2, and a fill factor of 85.9%. The performance was also tested by an unspecified “accredited testing center,” which certified it achieved an efficiency of 25.0%, an open-circuit voltage of 1.17 V, a short-circuit current density of 25.0 mA cm2, and a fill factor of 85.7%.
The cell was also found able to retain around 95% of its initial efficiency after 1,000 h and 90% for the same amount of hours under maximum power point tracking (MPPT). “This result indicates that the double-side 2D/3D heterojunctions have a significantly boosted energy barrier for ion migration, which might also improve the perovskite crystal stability,” the research group stated.
