Increasing climate problems need better solutions in terms of renewable energy harvesting devices. To beat the highest ever recorded, the researchers reveal that KAUST’s organic transport layer perovskite cell is 21.5% efficient.
The King Abdullah University of Science and Technology (KAUST), Saudi Arabia has invented a perovskite solar cell that is based on an organic electron transport layer (ETL). Also, for anchoring group researchers have used self-assembled monolayer (SAM) with phosphonic acid.
The cell achieved a power conversion efficiency of around 21.5% when tested under standard illumination conditions. According to the research team, this is the highest ever reported efficiency of a perovskite solar cell. That too of the one relying on an organic electron transporting layer.
The device achieves open-circuit voltage of 1.13V and short-circuit current density of 24.7 mA cm2. Lastly, it has a fill factor of about 77%.
Thermogravimetric analysis (TGA) conducted on these modified molecules revealed that they are thermally stable without much weight loss. Between 356° C and 268° C, average weight loss was only around 5%.
Stefaan De Wolf, lead author of the research, said, “All self-assembled monolayers were designed to collect holes, which works well for perovskite solar cells in the p-i-n polarity architecture.”
“Here, we tested a range of electron-selective SAMs designed and synthesized by Kaunas University of Technology and found that this works well in p-i-n polarity perovskite solar cells. So essentially the concept of SAM decoration of metal oxide to tune the charge selectivity has now been proven to work well for both polarities. Overall, this has quite some advantages, as for example low temperature processibility of the contacts.”
Preparation of the 21.5% Efficient Perovskite Solar Cell by KAUST
- Scientists use non-fullerene semiconductors composed of anthraquinone (AQ) and naphthalenediimide (NDI).
- The 2 modified molecular versions used were PAAQ and PANDI.
- According to them, this molecule allowed covalent binding with indium tin oxide (ITO) surfaces within the cell. This further led it to energetically match with the perovskite.
- The cell is build with an ITO and glass-based substrate.
- They also include electron-selecting SAMs, a hole transport layer (HTL) based on Spiro-OMeTAD, and a perovskite absorber. Also, a silver metal contacts with a molybdenum oxide (MoOx) layer.
Researchers stated, “UV–vis transmittance results of SAM functionalization on the ITO surface show negligible optical losses compared to bare ITO and ITO/SnO2 films.”
“In particular, PANDI-based SAMs demonstrate a higher surface homogeneity on the ITO surface than PAAQ SAMs. We found that the increasing surface homogeneity on the ITO/PANDI can effectively suppress nonradiative interfacial recombination through the field-effect passivation, as indicated by longer charge carrier lifetimes and higher QFLS values,” they further added.
Researchers further explained, “We also tested the operational stability of our SAM-based devices at 65 C with above 90% retention of their initial performance for 1000 h.”
They are considering PANDI SAMs as the most suitable future candidates of perovskite solar cells with p-i-n structures. This is because it is easy to apply them to flexible substrates.
“The PANDI-based device also showed improved operational long-term thermal stability, confirming that the PANDI SAM has a potential future to be utilized as ETL materials,” researchers concluded.
