Perovskite Solar - Page 68

Researchers from Professor Tan Hairen group at Nanjing University in China recently developed all-perovskite tandem solar cells with a conversion efficiency of 26.4%, certified by JET.

The team developed ammonium-cation-passivated Pb-Sn perovskites with long diffusion lengths, enabling subcells with an absorber thickness of ~1.2 μm. Molecular dynamics simulations suggest that widely-used phenethylammonium (PEA) cations are only partially adsorbed on the surface defective sites at perovskite crystallization temperatures. The passivator adsorption is predicted to be enhanced using 4-trifluoromethyl-phenylammonium (CF3-PA), which exhibits a stronger perovskite surface-passivator interaction than does PEA.

Scientists from TU Dresden, collaborating with researchers at Seoul National University (SNU) and Korea University (KU), have demonstrated the role of the re-use of photons ('photon recycling') and light scattering effects in perovskite solar cells, providing a pathway towards high-efficiency solar energy conversion.

The researchers from the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) at the TU Dresden observed the role of the photon recycling effect. When a photon is radiated inside re-absorbing semiconductors like perovskites, it can be re-absorbed by the emitter itself and generate a new photon via photoluminescence. Such a process of recursively re-absorbing and re-emitting the photons is called photon recycling. While this phenomenon has been previously demonstrated by several research groups, its practical contribution to the efficiency of perovskite solar cells has been under extensive debate. Based on the devices prepared by the groups in SNU and KU, the IAPP researchers discovered that photon recycling and light scattering effects greatly improve the light emission efficiency by a factor of ~5, significantly improving the photovoltage of perovskite solar cells.

The European Research Council (ERC) has awarded a €1.5 million Starting Grant to Professor Michael Saliba from the University of Stuttgart to support his research on perovskite thin films, where he will work on using light to control uncontrolled film growth.

Professor Saliba heads the Institute for Photovoltaics (IPV) in the German university. He has secured the grant for his LOCAL-HEAT project (Controlled Local Heating to Crystallize Solution-based Semiconductors for Next-Generation Solar Cells and Optoelectronics). He believes his research will enable the development of highly efficient perovskite solar cells that maintain their stability over several decades.

Researchers from China's Shaanxi Normal University and Chinese Academy of Sciences (CAS) have designed a perovskite solar cell with a novel defect passivation strategy based on the use of an ionic liquid (IL) perovskite capping layer.

ILs are non-molecular compounds that are composed solely of ions. They are said to possess several advantages over traditional organic solvents, such as negligible vapor pressure at room temperature and high thermal stability.

The Army Research Office and the Office of Naval Research have provided financial support for a new perovskite research, along with the National Science Foundation and the Energy Department's Office of Science. The researchers are a team of engineers working out of the lab of Aditya Mohite at Rice University.

The project was a collaborative one that also involved Purdue and Northwestern universities. The Energy Department was also involved via its Los Alamos, Argonne and Brookhaven laboratories. So were the Institute of Electronics and Digital Technologies in France, with additional support from the Academic Institute of France.

A consortium led by Hanwha Q Cells, a leading manufacturer of photovoltaic solar cells in South Korea, has been selected for a three-year state project to develop and commercialize perovskite crystalline silicon solar cells with high durability and high efficiency by using tandem cell technology that builds perovskite on top of silicon solar cells.

Tandem solar cells can be individual cells or connected in series, which are simpler to fabricate but the current is the same through each cell. Hanwha Q Cells said the consortium involving three private companies, two research bodies and three universities has signed an agreement with the state-run Korea Institute of Energy Technology Evaluation and Planning (KETEP) to develop module process technologies.

Researchers from the Diamond Light Source and the electron Physical Science Imaging Centre (ePSIC), Imperial College London, Yonsei University, Wageningen University and Research, and the University of Leeds have developed a method to stabilize perovskites without compromising their performance.

The researchers used an organic molecule as a 'template' to guide perovskite films into the desired phase as they form.

Researchers from the Hefei Institutes of Physical Science (HFIPS) under the Chinese Academy of Sciences (CAS), University of Science and Technology of China, North Minzu University, Hefei University of Technology, Greece's Institute of Nanoscience and Nanotechnology (INN) and Australia's Greatcell Energy have developed perovskite solar cells with a self-recovery capability and high stability in humid environment by introducing polymer called polyvinylpyrrolidone.

The team has shown that polyvinylpyrrolidone, a long chain insulating polymer, could form hydrogen bonds with ions in the cells and also prevent moisture in the air from invading perovskite materials. The hydrogen-bonding-initiated self-healing repairs the decayed perovskite solar cell back to the original state, continue to work, and alleviate long-term cell instability.

Researchers from Germany's Forschungszentrum Jülich have developed a planar perovskite solar cell that reportedly reached over 1,400'hours of operational stability at elevated temperatures. The 20.9% efficient device was built without the ionic dopants or metal oxide nanoparticles that are commonly used to contact the cell, as these can be subject to secondary reactions at higher temperatures.

The scientists tested many different perovskite mixtures before choosing the perovskite material for the cell, giving great focus to their thermal stability, using a self-constructed, high-throughput screening platform.

Researchers from Innovation Lab HySPRINT at Helmholtz-Zentrum Berlin (HZB) and Humboldt Universität zu Berlin (HU) have used an advanced inkjet printing technique to produce a large range of photodetector devices based on a hybrid perovskite semiconductor.

By mixing three inks, the researchers were able to precisely tune the semiconductor properties during the printing process. Inkjet printing is already an established fabrication method, allowing fast and cheap solution processing. Extending the inkjet capabilities from large area coating towards combinatorial material synthesis could open the door to new possibilities for the fabrication of different kinds of electronic components in a single printing step.