Researchers advance towards creating more stable blue perovskite LEDs

Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have developed blue LEDs based on metal halide perovskites, that, for the first time, uses asymmetrical bridges to hold the layers of perovskite together, creating a more stable structure.

OIST team finds that aymmetry is key to creating more stable blue perovskite LEDs image

“Perovskites have the potential to be a real game-changer in the lighting industry,” said first author Dr. Yuqiang Liu, a former post-doctoral researcher in the OIST Energy Materials and Surface Sciences Unit and currently a professor at Qingdao University, China. “In only a few short years, the efficiency of perovskite LEDs – how well they can transfer electrical energy into light energy – has shot up to a level that rivals traditional LEDs, and soon will surpass them.”

A piece of paper helps to fabricate perovskite solar cells

Researchers from Tor Vergata University and University of Zanjan have developed a new method that uses a simple sheet of paper to deposit the perovskite films without any expensive equipment. The way to achieve high performance with this low-cost method is to soak the paper applicator in anti-solvent which almost doubles efficiencies compared to when using it dry, reaching 11% on flexible plastic substrates. Paper, compared to other soft applicators, possesses the right porosity and smoothness for deposition of high quality perovskite films.

Simple and effective deposition method for solar cell perovskite films using a sheet of paper image

Most perovskite films in laboratories around the world are deposited through spin coating which guarantees high control of film thickness as well as morphology. However, most of the ink is expelled during deposition and is wasted. There have been efforts to develop coating techniques for deposition over large areas. The most efficient solar cells fabricated via spin coating involve adding drops of anti-solvent (i.e., a liquid with differing properties to those used in the perovskite precursor inks) during spinning which improves the morphological quality of the perovskite semiconductor films. This method is very difficult to implement when employing large area coating techniques, however, where the careful engineering of the drying processes involve heaters or gas flows to control the morphology of the perovskite film.

Researchers design solar cells made using perovskite and organic materials with a power conversion efficiency of 23.6%

A team of researchers from the National University of Singapore (NUS), the University of Hong Kong and Southern University of Science and Technology has reportedly "set a new record in the power conversion efficiency of solar cells made using perovskite and organic materials".

“The main motivation of this study is to improve the power conversion efficiency of perovskite/organic tandem solar cells. In our latest work, we have demonstrated a power conversion efficiency of 23.6% - this is the best performance for this type of solar cells to date,” said Dr. Chen Wei, Research Fellow at the NUS Department of Chemical and Biomolecular Engineering and the first author of this work.

Researchers develop all-perovskite tandem solar cells with 26.4% efficiency

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.

Researchers examine the role of photon recycling and scattering in perovskite solar cells

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.