Efficiency - Page 41

In a study announced last August, researchers from the Australian National University (ANU) reached an impressive 21.6% efficiency, which they said is the highest achieved for perovskite cells above a certain size. The details of their work, and the techniques used by the research team to achieve the results, have now been explained.

Lead researcher, associate professor Tom White, said the research team achieved the new record by adapting a technique previously used with traditional silicon-based solar cells that removed defects. 'A common problem with solar cells is that any defects in the cell can trap electrons, taking away the energy they gained by absorbing sunlight,' associate professor White said. 'A way around this is to 'passivate' the surface by coating the light absorbing material with a thin layer of another material to reduce defects. But the materials used to reduce defects are often poor conductors of electricity.'

Researchers from China have found that adding capsaicin, the molecule that makes chili peppers spicy, could improve perovskite-based solar cells' efficiency and stability.

"Considering the electric, chemical, optical, and stable properties of capsaicin, we preliminarily found that it would be a promising candidate," said Qinye Bao, senior author of the study. However, they needed to do some testing to find the ideal recipe. The researchers found, after executing their experiments, that 0.1 percent capsaicin by weight added to a MAPbl₃ perovskite precursor provided benefits.

Australian scientists at the University of Queensland have designed a perovskite solar cell based on a mix of 2D and 3D salts. By adding a fluorinated lead salt in the processing solution ' normally used to form 3D methylammonium lead iodide ' they were able to achieve a 21.1% efficiency, an open-circuit voltage of 1.12'V, a short-circuit current of 22.4'mA/cm², and a fill factor of 84%.

The scientists stated that the new cell is more moisture-resistant and durable than 'conventional' perovskite cells based on 3D materials alone. The cell is meant to include the advantages of cells based on two-dimensional (2D) perovskites, which generally provide more hydrophobicity and thermal stability than 'conventional' 3D structures. But it should also include the benefits of 3D perovskite cells, which can offer strong light absorption, good charge carrier transport, and higher power conversion efficiencies.

An international team of scientists, including ones from King Abdullah University of Science & Technology (KAUST) and University of Toronto, set out to increase the performance of solar panels by creating a bifacial (two-sided) tandem solar cell, made of perovskite and silicon materials.

Image credit: U of T

In outdoor environments, light primarily comes directly from the sun. Conventional tandem solar cells can already convert this light into electricity more efficiently compared to traditional silicon-only solar cells by absorbing additional wavelengths of light. Now, the researchers have realized that even more energy can be gathered using a two-sided tandem configuration. Light reflected and scattered from the ground ' referred to as 'albedo' ' can also be collected to significantly increase the current of a tandem solar cell. The new research outlines how the team engineered the perovskite/silicon device to exceed the currently accepted performance limits for the tandem configuration.

An international group of researchers, led by the University of Padova in Italy, has designed a hole extraction layer with water-splitting additives to reduce the impact of moisture in perovskite solar devices. They reported that the method ensured a power conversion efficiency of more than 9% in perovskite cells stored for a month in a water-saturated atmosphere.

There is an ongoing search for moisture stability in perovskite solar cells (PSCs), as protecting the perovskite layer from moisture is key to preventing excess water from forming on the layer itself and affecting overall performance. The new proposed solution to this issue integrates water-splitting (WS) hydrophobic layers to the perovskite absorber of a standard perovskite cell. The ancillary layers can purportedly convert incoming water into oxygen and hydrogen.

Oxford PV has reached a new efficiency world record for perovskite-silicon tandem cells at 29.52%, passing the previous record set less than a year ago by Helmholtz Zentrum Berlin. The new record has been certified by the U.S. National Renewable Energy Laboratory.

The new record was achieved on a cell measuring 1.12cm², produced in a laboratory setting. Oxford PV previously held the tandem cell efficiency record at 27.3%, and then 28%, before a group at Helmholtz Zentrum Berlin (HZB) pushed the record to 29.15% in January 2020. Both Oxford PV and HZB have stated that they have clear roadmaps to push this record beyond 30% in the near future.

A research team, led by Prof. LIU Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), recently reported high-efficiency perovskite solar cells with imidazolium-based ionic liquid for surface passivation and charge transport.

The quality of perovskite film plays a key role in device performance. Perovskite films are usually prepared by evaporating solvent from the precursor solution. However, defects often occur at the grain boundaries and on the surface during the crystallization process. These defects cause perovskite decomposition and non-radiative recombination, causing negative impacts on device performance. Surface passivation is considered as one of the most effective ways to reduce the number of defects due to its ease of application.

Researchers at HZB have published their recent work, reporting its current world record of 29.15% efficiency for a tandem solar cell made of perovskite and silicon. The tandem cell provided stable performance for 300 hours ' even without encapsulation. To accomplish this, the group, headed by Prof. Steve Albrecht, investigated physical processes at the interfaces to improve the transport of the charge carriers.

In the beginning of 2020, a team headed by Prof. Steve Albrecht at the HZB broke the previous world record for tandem solar cells made of perovskite and silicon (28.0%, Oxford PV), setting a new world record of 29.15%. Compared to the highest certified and scientifically published efficiency, this is a significant step forward. The new value has been certified at Fraunhofer ISE and listed in the NREL chart. Now, the results have been published in the journal Science with a detailed explanation of the fabrication process and underlying physics.

University of Tsukuba researchers examine the molecular-level processes taking place in perovskite solar cells when they are operating, to determine the factors that affect their performance.

The team explained that focusing on improving PCEs alone could be causing researchers to miss the significant steps forward that might result from a more detailed understanding of the underlying mechanisms. For example, the question of what causes the performance of perovskite solar cells to deteriorate is an important one that has not been comprehensively answered. External factors such as oxygen and moisture in the air are known to compromise perovskite layers. However, the internal changes that affect the performance of cells are not as well understood. The researchers have therefore probed the deterioration mechanism using electron spin resonance (ESR) spectroscopy.

Researchers from the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) in Germany have transferred a practical wetting tool for solution-based perovskite processing to a scalable printing technique.

On the basis of their recent publication on the development of a universal nanoparticle (NP) wetting agent for perovskite precursor solutions on nonwetting materials via spin coating, the team showed for the first time its transfer to scalable gas stream-assisted blade coating of solution-processed perovskite solar cells (PSCs) and modules in the inverted device architecture with highly hydrophobic poly(triaryl amine) (PTAA) as hole transport layer (HTL) on large-area substrates.