A5045723260- Perovskite Materials and Applications
- Solid-state spectroscopy and crystallography
- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Optical properties and cooling technologies in crystalline materials
- Strong Light-Matter Interactions
- X-ray Diffraction in Crystallography
- Quantum Chromodynamics and Particle Interactions
- 2D Materials and Applications
- Crystallization and Solubility Studies
- Quantum Electrodynamics and Casimir Effect
- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Magnetic and transport properties of perovskites and related materials
- Spectroscopy and Quantum Chemical Studies
- Organic and Molecular Conductors Research
- Atomic and Subatomic Physics Research
- Thermal Expansion and Ionic Conductivity
- Advanced Thermodynamics and Statistical Mechanics
- Mitochondrial Function and Pathology
- Photonic Crystals and Applications
- Luminescence Properties of Advanced Materials
- Molecular spectroscopy and chirality
- Advanced Thermoelectric Materials and Devices
- Thermal Radiation and Cooling Technologies
University of Oxford
2015-2023
Princeton University
2023
University of Warwick
2023
University of Cambridge
2014-2016
Durham University
1978
Abstract Phonon scattering limits charge-carrier mobilities and governs emission line broadening in hybrid metal halide perovskites. Establishing how charge carriers interact with phonons these materials is therefore essential for the development of high-efficiency perovskite photovoltaics low-cost lasers. Here we investigate temperature dependence four commonly studied formamidinium methylammonium perovskites, HC(NH 2 ) PbI 3 , PbBr CH NH discover that from longitudinal optical via Fröhlich...
Photovoltaic devices based on metal halide perovskites are rapidly improving in efficiency. Once the Shockley-Queisser limit is reached, charge-carrier extraction will be limited only by radiative bimolecular recombination of electrons with holes. Yet, this fundamental process, and its link material stoichiometry, still poorly understood. Here we show that methylammonium lead triiodide perovskite can fully explained as inverse process absorption. By correctly accounting for contributions to...
An understanding of the factors driving halide segregation in lead mixed-halide perovskites is required for their implementation tandem solar cells with existing silicon technology. Here we report that dynamics observed photoluminescence from CH3NH3Pb(Br0.5I0.5)3 strongly influenced by atmospheric environment, and encapsulation films a layer poly(methyl methacrylate) allows to be fully reversible repeatable. We further establish an empirical model directly linking amount fraction charge...
Double perovskites have recently emerged as possible alternatives to lead-based halide for photovoltaic applications. In particular, Cs2AgBiBr6 has been the subject of several studies because its environmental stability, low toxicity, and promising optoelectronic features. Despite these encouraging features, performances solar cells based on this double perovskite are still low, suggesting severe limitations that need be addressed. work we combine experimental theoretical show short electron...
We present a comprehensive study of the relationship between crystal structure and optoelectronic properties double perovskite Cs2AgBiBr6, which has emerged as promising candidate for photovoltaic devices. On basis single-crystal/powder X-ray diffraction neutron powder diffraction, we have revealed presence structural phase transition at Ts ≈ 122 K room-temperature cubic (space group Fm3̅m) new low-temperature tetragonal (I4/m). From reflectivity measurements found that peak exciton energy...
Cs2AgBiBr6 is a promising metal halide double perovskite offering the possibility of efficient photovoltaic devices based on lead-free materials. Here, we report evolution photoexcited charge carriers in using combination temperature-dependent photoluminescence, absorption and optical pump–terahertz probe spectroscopy. We observe rapid decays terahertz photoconductivity transients that reveal an ultrafast, barrier-free localization free time scale 1.0 ps to intrinsic small polaronic state....
Polaritonic states arise when a bright optical transition of molecular ensemble is resonantly matched to an cavity mode frequency. Here, we lay the groundwork study behavior polaritons in clean, isolated systems by establishing new platform for vibrational strong coupling gas-phase molecules. We access regime intracavity cryogenic buffer gas cell optimized preparation simultaneously cold and dense ensembles report proof-of-principle demonstration methane. strongly cavity-couple individual...
Traps limit the photovoltaic efficiency and affect charge transport of optoelectronic devices based on hybrid lead halide perovskites. Understanding nature energy scale these trap states is therefore crucial for development optimization solar cell laser technology materials. Here, low‐temperature photoluminescence formamidinium triiodide (HC(NH 2 ) PbI 3 investigated. A power‐law time dependence in emission intensity an additional low‐energy peak that exhibits anomalous relative Stokes shift...
Perovskite thin-film solar cells are one of the most promising emerging renewable energy technologies because their potential for low-cost, large-area fabrication combined with high conversion efficiencies. Recently, formamidinium lead triiodide (FAPbI3) and other (CH(NH2)2) based perovskites have been explored as interesting alternatives to methylammonium (MAPbI3) they exhibit better thermal stability. However, at present a major challenge is scale-up perovskite from small test-cells full...
Hybrid metal-halide perovskites have emerged as a leading class of semiconductors for optoelectronic devices because their desirable material properties and versatile fabrication methods. However, little is known about the chemical transformations that occur in initial stages perovskite crystal formation. Here we follow real-time formation dynamics MAPbI3 from bilayer lead iodide (PbI2) methylammonium (MAI) deposited through two-step thermal evaporation process. By lowering substrate...
Abstract Trap‐related charge‐carrier recombination fundamentally limits the performance of perovskite solar cells and other optoelectronic devices. While improved fabrication passivation techniques have reduced trap densities, properties states their impact on dynamics in metal‐halide perovskites are still under debate. Here, a unified model is presented radiative nonradiative channels mixed formamidinium‐cesium lead iodide perovskite, including trapping, de‐trapping accumulation, as well...
Since the emergence of lead halide perovskites for photovoltaic research, there has been mounting effort in search alternative compounds with improved or complementary physical, chemical, optoelectronic properties. Here, we report discovery Cu2AgBiI6: a stable, inorganic, lead-free wide-band-gap semiconductor, well suited use tandem photovoltaics. We measure very high absorption coefficient 1.0 × 105 cm–1 near onset, several times that CH3NH3PbI3. Solution-processed Cu2AgBiI6 thin films show...
Semiconducting polycrystalline thin films are cheap to produce and can be deposited on flexible substrates, yet high-performance electronic devices usually utilize single-crystal semiconductors, owing their superior electrical mobilities longer diffusion lengths. Here we show that the performance of metal-halide perovskites (MHPs) approaches single crystals at room temperature. Combining temperature-dependent terahertz conductivity measurements ab initio calculations uncover a complete...
Lead-free silver–bismuth semiconductors have become increasingly popular materials for optoelectronic applications, building upon the success of lead halide perovskites. In these materials, charge-lattice couplings fundamentally determine charge transport, critically affecting device performance. this study, we investigate properties recently discovered lead-free semiconductor Cu2AgBiI6 using temperature-dependent photoluminescence, absorption, and optical-pump terahertz-probe spectroscopy....
Formamidinium lead triiodide (FAPbI3) is the leading candidate for single-junction metal-halide perovskite photovoltaics, despite metastability of this phase. To enhance its ambient-phase stability and produce world-record photovoltaic efficiencies, methylenediammonium dichloride (MDACl2) has been used as an additive in FAPbI3. MDA2+ reported incorporated into lattice alongside Cl-. However, precise function role remain uncertain. Here, we grow FAPbI3 single crystals from a solution...
Understanding the mechanism of light-induced halide segregation in mixed-halide perovskites is essential for their application multijunction solar cells. Here, photoluminescence spectroscopy used to uncover how both increases temperature and light intensity can counteract process. It observed that, with increasing temperature, CH3 NH3 Pb(Br0.4 I0.6 )3 first accelerates toward ≈290 K, before slowing down again higher temperatures. Such reversal attributed trade-off between activation...
Successful chemical doping of metal halide perovskites with small amounts heterovalent metals has attracted recent research attention because its potential to improve long-term material stability and tune absorption spectra. However, some additives have been observed impact negatively on optoelectronic properties, highlighting the importance understanding charge-carrier behavior in doped perovskites. Here, we present an investigation trapping conduction films MAPbBr3 perovskite chemically...
Abstract The production of highly efficient single‐ and multijunction metal halide perovskite (MHP) solar cells requires careful optimization the optical electrical properties these devices. Here, precise control CH 3 NH PbI layers is demonstrated in cell devices through use dual source coevaporation. Light absorption device performance are tracked for incorporated MHP films ranging from ≈67 nm to ≈1.4 µm thickness transfer‐matrix modeling utilized quantify losses that arise interference...
Halogen mixing in lead-halide perovskites is an effective route for tuning the band gap light emission and multijunction solar cell applications. Here we report effect of halogen on optoelectronic properties from theory experiment. We applied virtual crystal approximation within density functional theory, GW approximation, Bethe–Salpeter equation to calculate structural, vibrational, a series mixed halide perovskites. separately perform spectroscopic measurements these analyze impact...
Formamidinium lead trioiodide (FAPbI3) is a promising perovskite for single-junction solar cells. However, FAPbI3 metastable at room temperature and can cause intrinsic quantum confinement effects apparent through series of above-bandgap absorption peaks. Here, we explore three common solution-based film-fabrication methods, neat N,N-dimethylformamide (DMF)-dimethyl sulfoxide (DMSO) solvent, DMF-DMSO with methylammonium chloride, sequential deposition approach. The latter two offer enhanced...
Abstract Silver‐bismuth based semiconductors represent a promising new class of materials for optoelectronic applications because their high stability, all‐inorganic composition, and advantageous properties. In this study, charge‐carrier dynamics transport properties are investigated across five compositions along the AgBiI 4 –CuI solid solution line (stoichiometry Cu x (AgBi) 1− I ). The presence close‐packed iodide sublattice is found to provide good backbone general semiconducting all...
Cavity coupling of gas-phase molecules will enable studies benchmark chemical processes under strong light-matter interactions with a high level experimental control and no solvent effects. We recently demonstrated the formation molecular polaritons by strongly bright ν3, J = 3 → 4 rovibrational transitions methane (CH4) to Fabry-Pérot optical cavity mode inside cryogenic buffer gas cell. Here, we further explore flexible capabilities this infrastructure. show that can greatly increase...
Lead halide perovskites are leading candidates for photovoltaic and light-emitting devices, owing to their excellent widely tunable optoelectronic properties. Nanostructure control has been central development, allowing improvements in efficiency stability, changes electronic dimensionality. Recently, formamidinium lead triiodide (FAPbI3) shown exhibit intrinsic quantum confinement effects nominally bulk thin films, apparent through above-bandgap absorption peaks. Here, we show that such...