Efficiency - Page 35

A group of scientists, led by Prof. Yiqiang Zhan from Fudan University, has reported high-efficiency flexible perovskite solar cells (f-PSCs) by annealing a SnO₂ ETL in a rough vacuum at a low temperature (100 '), and peak efficiency reached 20.14%.

SnO₂ layers that have been prepared by this method have shown higher robustness and hydrophobicity in comparison with samples prepared in an air atmosphere and temperatures of 100 °C, leading to an improved ETL/perovskite interface connection and reducing defects in the SnO₂/perovskite interface. The appropriate density of oxygen vacancies on the surface during this treatment can be responsible for higher conductivity, which is beneficial for charge transfer.

In October 2021, The Perovskite-Info team met Cyprus University of Technology's (CUT) Professor Stelios Choulis, who kindly agreed to show us around his workspace and labs and update us on his team's ongoing work.

Choulis, Professor of Material Science and Engineering at the Cyprus University of Technology, is also the founder and head of the Molecular Electronics and Photonics (MEP) Research Unit. With work in UK, Germany and the Silicon Valley (USA) under his belt, Choulis is a highly skilled and experienced researcher in the fields of both photovoltaics and OLEDs. He also participated and led several large-scale research programs (ERC-Consolidator Grant European Horizon project, SME-EU FP7, RIF and RPF-Cyprus, BMBF-Germany, DOE-USA).

An international team of researchers recently tested a new way of passivating defects in perovskite solar cells. Using a tailored arrangement of atoms, the team managed to overcome challenges related to the formation of a two-dimensional perovskite layer on top of the active cell material, and reach 21.4% conversion efficiency for a 26cm² active area, which is said to be a record for a perovskite device of this size.

Passivation layers, deposited on top of the perovskite material, play an essential role in reducing material defects and unwanted reactions within the material, to improve both performance and stability. One strategy that has been found effective is the use of alkylammonium halides. In many cases these form an additional two-dimensional perovskite layer on top of the perovskite, which can improve device stability but also negatively affect performance.

Scientists in Germany's Karlsruhe Institute of Technology (KIT) have applied vapor-based deposition techniques and laser scribed interconnection (well established processes in existing thin-film solar manufacturing) to fabricate perovskite mini modules which achieved a maximum efficiency of 18% for a device measuring 4cm².

The team believes that based on these processes, it would be possible to simplify processing and reduce losses associated with scaling up to commercial-sized devices.

Solliance recently announced that a collaboration with the M2N group of René Janssen at University of Technology Eindhoven has resulted in two world-records for 4T perovskite tandems.

The partners reported that they further optimized the wide-bandgap (1.69eV) perovskite cells with high near-infrared transparency for 4T tandem applications. The perovskite cell has reached a stabilized efficiency of 17.8% during 5-min maximum-power-point tracking. In combination with the Panasonic silicon bottom cell, a new world-record 4T perovskite/Si tandem efficiency of 29.2% was realized.

Researchers at South Korea's Ulsan National Institute of Science and Technology (UNIST) and Pohang University of Science and Technology report a power conversion efficiency of 25.8% for a single junction perovskite solar cell, by forming a coherent interlayer between electron-transporting and perovskite layers to reduce interfacial defects.

The cell was built with an interlayer between a tin(IV) oxide (SnO₂) electron-transporting layer and a layer made of a halide perovskite layer by coupling chlorine-bonded SnO₂ with a perovskite precursor containing chlorine. 'This interlayer has atomically coherent features which enhance charge extraction and transport from the perovskite layer; and fewer interfacial defects,' the academics explained.

The US Department of Energy (DoE) awarded nearly $40 Million for grid-decarbonizing solar technologies projects. The DoE awarded the funds to 40 research projects, several of which are perovskite related. We'll list the perovskite projects (which were awarded a total of $1.25 million) below.

The DoE also issued a request for information (RFI) to gather input on efficiency, stability and replicability performance targets for perovskite photovoltaic devices that could be utilized to demonstrate technical and commercial readiness for future funding programs.

Researchers at UC Santa Barbara recently conducted a research that disproved the common belief that organic molecules are crucial to achieving PSCs' impressive performance because they suppress defect-assisted carrier recombination. Not only was this assumption shown to be incorrect, but the team also found that all-inorganic materials have the potential for outperforming hybrid perovskites.

“To compare the materials, we performed comprehensive simulations of the recombination mechanisms,” explained Xie Zhang, lead researcher on the study. “When light shines on a solar-cell material, the photo-generated carriers generate a current; recombination at defects destroys some of those carriers and hence lowers the efficiency. Defects thus act as efficiency killers.”

Saule Technologies' perovskite-based PV cells have reached 25.5% efficiency, as confirmed by laboratory measurements at the Fraunhofer ISE group of Dr. Uli Würfel.

The measurements were carried out under 1000 lux illumination by a cold white LED, which represents the real-life environment for the first commercial application of these devices.

Researchers at the University of Rome Tor Vergata's Centre for Hybrid and Organic Solar Energy (CHOSE) and ISM-CNR have tested a commercially available HTM with a new core made by low-cost fluorene'xantene units. The experimentation was conducted on small (0.09 cm²) and large area (1.01 cm²) cells.

The one-pot synthesis of this compound is said to drastically reduce its cost compared with the commonly used Spiro-OMeTAD. The optoelectronic performances and properties were characterized through JV measurement, IPCE (incident photon to current efficiency), steady-state photoluminescence and ISOS stability test. SEM (scanning electron microscope) images reveal a uniform and pinhole free coverage of the X55 HTM surface, which reduces the charge recombination losses and improves the device performance relatively to Spiro-OMeTAD from 16% to 17%. The ISOS-D-1 stability test on large area cells without any encapsulation reports an efficiency drop of about 15% after 1000 h compared to 30% for the reference case.