Efficiency - Page 37

Researchers from the University of North Carolina have developed a mini perovskite solar module with a power conversion efficiency of up to 19.3% efficiency based on a novel approach for interface engineering.

The new device was created using a new technique for stabilizing the embedded perovskite-substrate interfaces in the solar cells. Common approaches, the researchers explained, had previously focused on stabilizing perovskite-metal electrode interfaces through surface passivation or post-fabrication treatment. 'Degradation of perovskite solar cells starts from the interfaces, including both perovskite-metal electrodes and perovskites-substrates, where defects enrich,' the team stated in the new paper. 'Stabilizing the embedded bottom interfaces is as important as that of [the] top interface.'

Researchers at KAUST have developed a multifunctional molecule that can plug various atomic-scale defects in perovskite solar materials, which could significantly boost the longevity and electrical output PSCs.

Perovskites inevitably feature defects, such as where a particular ion did not slot into place during fabrication, leaving a gap in the structure. These reactive sites can contribute to rapid performance decline — unless they can be fixed. “Defect passivation is very important for improving the long-term stability of perovskite solar cells,” says Furkan Isikgor, a researcher in Stefaan De Wolf’s group.

Researchers from Kanazawa University in Japan have found that the addition of cesium iodide can improve the stability and efficiency of certain perovskite solar cells. Added to MAPbI₃ cells by alternately depositing thin layers of MAPbI₃ and CsI, atoms from Cs migrate and become intercalated into the crystal lattice.

'Our approach allowed us to produce layers with precise control over the CsI intercalation,' said researcher Tetsuya Taima. Using this control, different Cs-inclusive perovskite crystals were created.

Researchers from Korea and Vietnam have developed and designed a bifacial four-terminal perovskite/crystalline silicon heterojunction tandem solar cell configuration albedo reflection in which the c-Si HJ bottom sub-cell absorbs the solar spectrum from both the front and rear sides (reflected light from the background such as green grass, white sand, red brick, roofing shingle, snow, etc.).

This approach reportedly achieved an outstanding conversion efficiency exceeding 30%, higher than those of both the top and bottom sub-cells. Notably, this efficiency is also greater than the Schockley'Quiesser limit of the c-Si solar cell (approximately 29.43%). The proposed approach has the potential to lower industrial solar cell production costs in the near future.

Philipp Tockhorn from Helmholtz-Zentrum Berlin (HZB) recently presented his team's work at the virtual OSA Advanced Photonics Congress (July 26th to 30th, 2021). In this new work, the researchers used simulation and experiments to illustrate that introducing a small nanoscale texturing on the surface of materials in perovskite or silicon tandem solar cells can raise the efficiency above 29%, by decreasing the amount of light energy lost by reflection.

The researchers presented nanotextured perovskite/silicon tandem solar cells that are on par with the best cells presented to date. These findings may contribute to the further development of highly efficient perovskite/silicon tandem solar cells and have the potential to further decrease the cost of solar electricity.

A team of researchers, led by the University of Sydney, have used a new approach that could be the key to producing low cost and environmentally friendly perovskite solar cells, while achieving a new efficiency milestone for these cells.

The researchers said they had made crucial improvements to the process of 'gas quenching' to fabricate perovskite thin films. The research team successfully demonstrated a steady-state conversion efficiency of 23.6%, which they claim is the highest efficiency achieved for perovskite solar cells produced using the 'gas quenching' technique.

Researchers at the Swiss Federal Institute of Technology in Lausanne (EPFL) and Northwestern Polytechnical University in China have fabricated an inverted perovskite solar cell based on a star-shaped polymer that can reportedly improve charge transport and inhibit ion migration at the perovskite interface.

Schematic diagram of the interaction between the PPP polymer (partial 3D structure) and perovskite. Image from ScienceAdvances

The cell has a 'p-i-n' layout and is based on a perovskite material known as CsMAFA modified with a polymer called polyhedral oligomeric silsesquioxane-poly(trifluoroethyl methacrylate)-b-poly(methyl methacrylate) or simply PPP polymer.

Researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, in collaboration with University of Toronto, the National University of Singapore and National Technical University of Athens, have designed monolithic tandem solar cell with power conversion efficiency of 27%, surpassing the previous best reported value of 22% in the same configuration.

The team explains that translating the high power conversion efficiencies of single-junction perovskite solar cells in their classic, non-inverted (n'i'p) architecture to efficient monolithic n'i'p perovskite/silicon tandem solar cells with high current densities has been a persistent challenge due to the lack of low-temperature processable, chemically-insoluble contact materials with appropriate polarity and sufficient optical transparency. To address this, they developed sputtered amorphous niobium oxide (a-NbOx) with ligand-bridged C60 as an efficient electron-selective contact, deposited on the textured-silicon bottom cell.

researchers at the Okinawa Institute of Science and Technology Graduate University (OIST), led by Professor Yabing Qi, have demonstrated that creating a raw material used for perovskite solar cells in a different way could be key to the success of these cells.

'There's a necessary crystalline powder in perovskites called FAPbI₃, which forms the perovskite's absorber layer,' explained one of the lead authors, Dr. Guoqing Tong, Postdoctoral Scholar at OIST. 'Previously, this layer was fabricated by combining two materials ' PbI₂ and FAI. The reaction that takes place produces FAPbI₃. But this method is far from perfect. There are often leftovers of one or both of the original materials, which can impede the efficiency of the solar cell.'

Researchers at the Dresden University of Technology (TUD) have announced the fabrication of a solar cell based on all-inorganic cesium-lead iodide (CsPbI₃) perovskite, which is also sometimes referred to as 'black perovskite'.

a) Schematic of the deposition procedure (b) device structure. Image from Advanced Energy Materials

TUD researcher Yana Vaynzof said that the choice of this specific material was motivated by the fact that it shows superior stability as compared to the commonly used organic-inorganic lead halide perovskites.