Researchers from Korea University and Seoul Women's University have developed an inverted perovskite solar cell by introducing an electron-accepting interlayer at the interface between the perovskite layer and the electron transport layer.
The solar cell has a p-i-n structure (the perovskite cell material is deposited onto the hole transport layer and then coated with the electron transport layer), which is the opposite of the conventional n-i-p device structure. Inverted perovskite solar cells tend to show good stability, but lack in terms of conversion efficiency and cell performance.
The scientists created the electron-accepting interlayer with a light-harvesting material known as 3,4,9,10-perylenetetracarboxylic diimide (PDI) and carbon black (CB), a 3D cluster compound composed of boron, carbon, and hydrogen atoms. They varied the thickness of the PDI–Cb interlayer from 0 to 3.0 nm. The research group built the cell using an indium tin oxide (ITO) substrate, a solution based on poly(triaryl)amine (PTAA), which is an excellent hole transporting and electron blocking material, the perovskite layer, the PDI–Cb interlayer, an electron transport layer made of buckminsterfullerene (C60), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
The team measured the performance of the device under standard illumination conditions and found it achieved a power conversion efficiency of 22.31%, an open-circuit voltage of 1.16 V, a short-circuit current of 23.81 mA/cm2, and a fill factor of 80.70%. A reference device without the PDI–Cb interlayer reached an efficiency of 19.98%, an open-circuit voltage of 1.1 V, a short-circuit current of 22.86 mA/cm2, and a fill factor of 78.74%.
“The devices adopting PDI–Cb interlayer showed enhanced device performance with increasing thickness of the PDI–Cb interlayer and reached peak photovoltaic performance at the PDI–Cb thickness of 2.0 nm,” the team said. “The PDI–Cb interlayer acts not only as a good electron acceptor due to o-Cb unit but also as charge transport due to slip-stacked packing structure.
The scientists said the cell was also able to retain 91.7% of its initial efficiency after 1,000 h under standard illumination conditions.
