Perovskite crystals, with their exceptional nonlinear optical properties, lasing and waveguiding capabilities, could offer a promising platform for integrated photonic circuitry within the strong-coupling regime at room temperature.

Researchers at the University of Warsaw, CNR Nanotec, Łukasiewicz Research Network—Institute of Microelectronics and Photonics, Łódź University of Technology and Polish Academy of Sciences have demonstrated a versatile template-assisted method to efficiently fabricate large-scale waveguiding perovskite crystals of arbitrarily predefined geometry such as microwires, couplers and splitters. 

BusinessKorea reports that researchers at the Ulsan National Institute of Science and Technology (UNIST) have significantly improved the efficiency and stability of perovskite solar cells by addressing defect issues.

Schematic of perovskite crystallinity changes and thickness-based photoluminescence analysis through the introduction of bidirectional tuning molecules. Source: BusinessKorea, UNIST

The UNIST team announced that a joint research team, led by Professors Kim Jin-young and Kim Dong-seok from the Department of Energy and Chemical Engineering, and Professor Lee Geun-sik from the Department of Chemistry, successfully introduced bidirectional tuning molecules between the perovskite photoactive layer and the electron transport layer.

An international team of researchers, including ones from the University of Toronto, University of Toledo, Northwestern University, Lawrence Berkeley National Laboratory, KAUST and more, recently developed an all-perovskite tandem device that is said to show reduced recombination losses in the cell’s bottom device and excellent stability.

Image credit: Northwestern University
 

To improve the perovskite solar cell’s surface, the scientists created partially non-conductive and non-functional areas that protect the perovskite area underneath from becoming defective. The team examined the addition of diamine to improve the perovskite solar cell’s surface. The scientists found that the process made the surface more stable and improved the overall performance, resulting in a power conversion efficiency of 27.4% with better stability.

Researchers from China's Beijing Institute of Technology, Peking University, Central South University, Jiangnan University and Auner Technology have developed a unique binary 2D perovskite passivation approach and used it to fabricate a monolithic perovskite/silicon tandem solar cell with a steady-state efficiency of 30.65% (reportedly assessed by a third party). 

Schematic of the monolithic tandem structure based on a double-side textured silicon heterojunction cell. Image credit: Nature Communications

The tandem devices also retained 96% of their initial efficiency after 527 h of operation under full spectral continuous illumination, and 98% after 1000 h of damp-heat testing (85 °C with 85% relative humidity).

Researchers from North China Electric Power University, Beijing University of Chemical Technology and Sichuan Normal University have created bright blue perovskite LEDs (PeLEDs), among the LED colors needed to enable commercial applications.

With high efficiency and stability, PeLEDs could be a promising new option for full-color displays and solid-state lighting technology. However, while red and green PeLEDs have nearly reached their theoretical external quantum efficiencies, blue PeLEDs do not yet reach the efficiency, stability, or luminosity required for commercial applications. The novel method presented in this work seeks to address this challenge. Using an in situ spin-coating method, the authors created Dion-Jacobson phase quasi-2D perovskite nanocrystals. A mixture of mixed inorganic cesium bromide and two organic bidentate molecules in the perovskite precursor solution regulates growth and crosslinking in the nanocrystals. The resulting perovskites demonstrated effective emission in PeLEDs, brightly glowing from sky blue to deep blue.

Colloidal perovskite nanoplatelets (NPLs) have shown promise in tackling blue light-emitting diode challenges based on their tunable band gap and high photoluminescence efficiencies. However, high quality and large area dense NPL films have been proven quite hard to prepare due to their chemical and physical fragility during the liquid phase deposition.

Recently, researchers from University of Groningen reported a perovskite-polymer composite film deposition strategy with fine morphology engineering obtained using the blade coating method. The effects of the polymer type, solution concentration, compounding ratio and film thickness on the film quality were systematically investigated and the team found that a relatively high-concentration suspension with an optimized NPL to polymer ratio of 1 : 2 is crucial for the suppression of phase separation and arriving at a uniform film.

Metal halide perovskite light-emitting diodes (PeLEDs) that emit deep-blue color with high efficiency have not yet been fully achieved and become more difficult in the thin film of confined perovskite colloidal quantum dots (PeQDs) due to particle interaction. Recently, researchers from Seoul National University and University of Toronto demonstrated that electronic coupling and energy transfer in PeQDs induce redshift in the emission by PeQD film, and consequently hinder deep-blue emission.

Scheme illustrating QD-QD interaction related to emission spectrum shifts in the A) QD-only film and B) QD-mCP solid solution. Image credit: Advanced Materials

To achieve deep-blue emission by avoiding electronic coupling and energy transfer, a QD-in-organic solid solution was introduced, to physically separate the QDs in the film. This physical separation of QDs reduces the interaction between them yielding a blueshift of ≈7 nm in the emission spectrum. 

Scientists at Oxford University Physics Department have developed thin-film perovskite coatings that could be placed onto the surfaces of everyday objects like cars and mobile phones to generate increasing amounts of solar electricity without the use of silicon-based solar panels.

Dr Shuaifeng Hu, Post Doctoral Fellow at Oxford University Physics, holding the new thin-film perovskite material. Image credit: Martin Small and Oxford University.

The light-absorbing material is said to be, for the first time, thin and flexible enough to apply to the surface of almost any building or common object. Using a pioneering technique developed in Oxford, which stacks multiple light-absorbing layers into one solar cell, they have harnessed a wider range of the light spectrum, allowing more power to be generated from the same amount of sunlight.

Researchers from Queen Mary University of London and QinetiQ could pave the way for faster discovery of novel perovskite materials with desirable properties for applications in wireless communication and biosensors. The recent research introduces an automated platform for rapid sintering and dielectric characterization of perovskite solid solutions. This innovative approach integrates machine learning (ML) for material screening with robotic synthesis and high-throughput characterization.

The scientists stated that while accelerating perovskite solid solution discovery and sustainable synthesis is crucial for addressing challenges in wireless communication and biosensors, the vast array of chemical compositions and their dependence on factors such as crystal structure and sintering temperature require time-consuming manual processes. To overcome these constraints, they introduced an automated materials discovery approach encompassing machine learning (ML) assisted material screening, robotic synthesis, and high-throughput characterization. 

Solar cells and light-emitting diodes strive to maintain the excited state kinetics of molecules. A major loss mechanism, especially in the highest efficiency systems, is called exciton-exciton annihilation, leading to lowering of solar efficiency and of light output in LEDs. Controlling the amount of exciton-exciton annihilation is therefore an important goal that affects efficiency.

National Renewable Energy Laboratory (NREL) researchers, working with researchers from University of Colorado Boulder, sought to control exciton/exciton annihilation by coupling excitons with cavity polaritons, which are essentially photons caught between two mirrors, to combat energy dissipation and potentially increase efficiency in optoelectronic devices. As detailed in their recent article, the scientists used transient absorption spectroscopy to demonstrate control of the loss mechanism by varying the separation between the two mirrors forming the cavity enclosing the 2D perovskite (PEA)₂PbI₄ (PEPI) layer. This perovskite material is a candidate for future LED applications.