Perovskite applications - Page 2

Rice University researchers have developed highly water-stable SiO₂-coated halide perovskite nanocrystals (HPNCs) as efficient photocatalysts for antimicrobial applications. The double SiO₂ layer coating method confers long-term structural and optical stability to HPNCs in water, while the in situ synthesis of lead- and bismuth-based perovskite NCs into the SiO₂ shell enhances their versatility and tunability. 

Image from: Nano Letters 

The team demonstrated that the substantial generation of singlet oxygen via energy transfer from HPNCs enables efficient photoinduced antibacterial efficacy under aqueous conditions. More than 90% of Escherichia coli was inactivated under mild visible light irradiation for 6 h. The excellent photocatalytic antibacterial performance suggests that SiO₂-coated HPNCs hold great potential for various aqueous phase photocatalytic applications.

Researchers from Canada's University of Waterloo and University of Toronto have developed a tiny, wearable piezoelectric generator based on perovskites that can generate electricity from vibrations or body movements. The technology could potentially charge laptops by typing or power a smartphone’s battery from the movements of a run, for instance. 

The device makes use of the piezoelectric effect, which generates electrical energy by applying pressure to materials like crystal and certain ceramics.  The tea, explained that older materials are brittle, expensive and have a limited ability to generate electricity, as opposed to the materials created for the new generator - which are flexible, more energy-efficient and cost less.

Researchers from the University of Oxford, University of Manchester,  University of Sheffield and Helmholtz-Zentrum Berlin (HZB) have developed a high volatility, low toxicity, biorenewable solvent system to fabricate a range of 2D perovskites, which can be used as effective precursor phases for subsequent transformation to α-formamidinium lead triiodide (α-FAPbI₃), fully processed under ambient conditions. 

This solvent system is meant to address challenges involved with producing perovskite solar cells (PSCs) via high-throughput coating methods, such as the use of harmful solvents, the expense of maintaining controlled atmospheric conditions, and the inherent instabilities of PSCs under operation. 

Researchers from Nanyang Technological University (NTU) and The Hong Kong Polytechnic University, led by Associate Professor Nripan Mathews of NTU’s School of Materials Science and Engineering, have synthesized four unique types of 2D halide perovskites.

Dr. Ayan Zhumekenov, a research fellow at the school and lead author of the study, used a novel approach to create the new perovskites by incorporating dimethyl carbonate – a non-toxic solvent – into methylammonium-based perovskite crystals. By analyzing the new crystal structures, the scientists discovered that the structures’ band gap could be tuned by adjusting the ratio of methylammonium to dimethyl carbonate in them. The band gap, which determines 
the color of the material, is the energy required for an electron to break free from its bound state and become conductive.

Researchers from King Abdullah University of Science and Technology (KAUST), the University of Manchester and Marvell Semiconductor have developed an innovative high-speed photodetector design utilizing ultrathin two-dimensional metal halide perovskites (2D-MHP), coupled with a planar nanocavity to significantly enhance optical absorptance—achieving more than a fourfold increase in a solution-processed 10-nm-thick 2D-MHP film. 

This integration facilitates an exceptional response time (30 ns) alongside a high responsivity of 2.12 A W⁻¹. The method is said to overcome traditional constraints related to thickness and absorption, thereby optimizing device speed and dark noise features through active area variation.

Chinese Academy of Sciences (CAS) researchers believe that the issue of instability of perovskite solar cells (PSCs) primarily originates from the migration of halide ions—particularly iodide ions (I⁻). Under light exposure and thermal stress, I⁻ migrates and transforms into I₂, leading to irreversible degradation and performance loss. 

To tackle this challenge, the team introduced the additive 2,1,3-benzothiadiazole,5,6-difluoro-4,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) (BT2F-2B) into the perovskite. The strong coordination between the unhybridized p orbital and lone-pair electrons from I⁻ inhibits the deprotonation of MAI/FAI and the subsequent conversion of I⁻ to I₂. The highly electronegative fluorine enhances its electrostatic interaction with I⁻. Consequently, the synergistic effect of BT2F-2B effectively suppresses the decomposition of perovskite and the defect density of the iodide vacancies. 

Researchers from King Abdullah University of Science and Technology (KAUST) set out to develop X-ray detection technology with reduced radiation dosage without compromising detection efficiency. The team developed a cascade-engineered approach that uses two interconnected single-crystal devices to mitigate dark current and enhance the detection limit. 

Using methylammonium lead bromide (MAPbBr₃) perovskite single crystals, the scientists engineered devices that significantly reduced detection thresholds and improved signal-to-noise ratios (SNRs). 

Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL), North China Electric Power University, Westlake University, Lomonosov Moscow State University and others have described the addition of N,N-dimethylmethyleneiminium chloride ([Dmei]Cl) into perovskite precursor solutions to produce two cations in situ—namely 3-methyl-2,3,4,5-tetrahydro-1,3,5-triazin-1-ium ([MTTZ]⁺) and dimethylammonium ([DMA]⁺) cations - that enhanced the photovoltaic
performance and stability of perovskite solar modules.  

A schematic of the roles of [MTTZ]⁺ and [DMA]⁺ in the 3D perovskite matrix. Image from: Science

The team explained that the in situ formation of [MTTZ]⁺ cation increased the formation energy of iodine vacancies and enhanced the migration energy barrier of iodide and cesium ions, which suppressed nonradiative recombination, thermal decomposition, and phase segregation processes. 

The formation of a homogeneous passivation layer based on phase-pure two-dimensional (2D) perovskites is a challenge for perovskite solar cells, especially when upscaling the devices to modules. Researchers from China's Wuhan University of Technology, Xidian University, University of Electronic Science and Technology of China and Germany's Technical University of Munich have revealed a chain-length-dependent and halide-related phase separation problem of 2D perovskite growing on top of three-dimensional perovskites. 

The scientists have demonstrated that a homogeneous 2D perovskite passivation layer can be formed upon treatment of the perovskite layer with formamidinium bromide in long-chain ( >10) alkylamine ligand salts. 

Researchers from Zhejiang University, Soochow University, King Abdullah University of Science and Technology (KAUST), The Hong Kong Polytechnic University and Suzhou Maxwell Technologies have addressed common challenges related to hole transport layers that are commonly used for the perovskite top cells, such as defects, non-conformal deposition or de-wetting of the overlying perovskite on the textured silicon bottom cells.

The team decided to develop a strategy based on co-deposition of copper(I) thiocyanate and perovskite, where effective perovskite grain boundary passivation and efficient hole collection are simultaneously achieved by the embedded copper(I) thiocyanate, which creates local hole-collecting contacts. Fabricated monolithic perovskite/silicon tandem devices achieved a certified power conversion efficiency of 31.46% for 1 cm² area devices.