A5000107643- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Perovskite Materials and Applications
- Thin-Film Transistor Technologies
- Quantum Dots Synthesis And Properties
- Phase-change materials and chalcogenides
- Liquid Crystal Research Advancements
- Advanced Polymer Synthesis and Characterization
- Chalcogenide Semiconductor Thin Films
- Nanowire Synthesis and Applications
- Molecular Junctions and Nanostructures
- Rheology and Fluid Dynamics Studies
- Organic Light-Emitting Diodes Research
- Polymer Nanocomposites and Properties
- Block Copolymer Self-Assembly
- Carbon Nanotubes in Composites
- Solid-state spectroscopy and crystallography
- Polymer composites and self-healing
- Polymer Surface Interaction Studies
- Chemical and Physical Properties of Materials
- Optical Polarization and Ellipsometry
- Nanoparticle-Based Drug Delivery
- Chemical Thermodynamics and Molecular Structure
- Nonlinear Photonic Systems
- Glass properties and applications
University of Oxford
2017-2024
University of Arizona
2022
University of Florence
2022
Oxfam
2020
Pennsylvania State University
2012-2017
Ultralow trap densities, exceptional optical and electronic properties have been reported for lead halide perovskites single crystals; however, ambiguities in basic properties, such as the band gap, defect densities bulk at surface prevail. Here, we synthesize crystals of methylammonium bromide (CH3NH3PbBr3), characterise absorption photoluminescence show that are almost identical to those polycrystalline thin films. We observe significantly longer lifetimes carrier diffusion plays a...
Vegetable oils are an attractive source for polymers due to their low cost, abundance, annual renewability, and ease of functionalization. Stearyl lauryl acrylate, derived from vegetable such as soybean, coconut, palm kernel oil, have been polymerized through reversible addition–fragmentation chain transfer polymerization, resulting in poly(styrene-b-(lauryl acrylate-co-stearyl acrylate)-b-styrene) (SAS) triblock copolymers. Varying the length side on polyacrylate midblock (C18 C12 stearyl...
The effectiveness of new a electron acceptor for organic solar cells is demonstrated. homoleptic zinc(II) complex 2,6-diphenylethynyl-1,3,7,9-tetraphenylazadipyrromethene. high power-conversion efficiency obtained attributed to the acceptor's 3D structure, which prevents crystallization and promotes favourable nanoscale morphology, its Voc, ability contribute light harvesting at 600–800 nm.
The complex microstructure of organic semiconductor mixtures continues to obscure the connection between active layer morphology and photovoltaic device performance. For example, ubiquitous presence mixed phases in polymer/fullerene solar cells creates multiple morphologically distinct interfaces which are capable exciton dissociation or charge recombination. Here, it is shown that domain compositions fullerene aggregation can strongly modulate photogeneration at ultrafast timescales through...
Through a combination of X-ray scattering and energy-filtered electron microscopy, we have quantitatively examined the relationship between mesostructure photoactive layer device performance in PBTTT/PC71BM solar cells. We can predict from structural data through simple morphological model which includes exciton diffusion length.
Resonant soft X-ray scattering (RSOXS) is a complementary tool to existing reciprocal space methods, such as grazing-incidence small-angle scattering, for studying order formation in polymer thin films. In particular, RSOXS can exploit differences absorption between multiple phases by tuning the energy one or more resonance peaks of organic materials containing carbon, oxygen, nitrogen, other atoms. Here, we have examined structural evolution...
Periodic media are fundamentally important for controlling the flow of light in photonics. Recently, emerging field non-Hermitian optics has generalized notion periodic to include a new class materials that obey parity-time (PT) symmetry, with real and imaginary refractive index variations transform into one another upon spatial inversion, leading variety unusual optical phenomena. Here, we introduce simple approach based on interference lithography oblique angle deposition achieve...
We present a crystallographic and optoelectronic study of the double perovskite Cs2AgBi1–xInxBr6. From structural characterization we determine that indium cation shrinks lattice shifts cubic-to-tetragonal phase transition point to lower temperatures. The absorption onset is shifted shorter wavelengths upon increasing content, leading wider band gaps, which rationalize through first-principles structure calculations. Despite unfavorable gap shift, observe an enhancement in steady-state...
Abstract Free charge generation after photoexcitation of donor or acceptor molecules in organic solar cells generally proceeds via (1) formation transfer states and (2) their dissociation into separated states. Research often either focuses on the first component combined effect both processes. Here, we provide evidence that state rather than presents a major bottleneck for free fullerene-based blends with low energetic offsets between singlet We investigate devices based dilute content...
Block copolymer micelles enable the formation of widely tunable self-assembled structures in liquid phases, with applications ranging from drug delivery to personal care products nanoreactors. In order understand fundamental aspects micelle assembly and dynamics, structural properties solvent uptake biocompatible poly(ethylene oxide-b-ε-caprolactone) (PEO–PCL) diblock copolymers deuterated water (D2O)/tetrahydrofuran (THF-d8) mixtures were investigated a combination small-angle neutron...
Phase-change materials, such as the well-known ternary alloy Ge 2 Sb Te 5 , are essential to many types of photonic devices, from re-writeable optical disk memories more recent developments phase-change displays, reconfigurable metasurfaces, and integrated devices systems. The successful design development applications requires accurate knowledge complex refractive index material being used. To this end, it is common practice rely on published experimental data. However, values can vary...
Mesoscopic structural length scales in the photoactive layer of organic solar cells affect exciton dissociation into charges and thus device performance. It is currently hypothesized that these are largely affected by processing conditions such as annealing temperature, time, casting solvent. In our study, we utilized grazing incidence small-angle X-ray scattering energy-filtered transmission electron microscopy to characterize in-plane morphology...
Interfacial barriers at electrode–semiconductor contacts can greatly limit charge collection efficiency and hamper device performance. Doping of the semiconductor near interface mitigate extraction or injection problems by allowing tunneling through with reduced width. Here we demonstrate that polymer acids act as p-type dopants electrode interfaces for active layers containing poly(3-hexylthiophene-2,5-diyl) (P3HT). By varying pendant acidic groups between aromatic sulfonic acid,...
A microphase-separated poly(styrene-b-(lauryl-co-stearyl acrylate)-b-styrene) (SAS) triblock copolymer exhibiting a disordered spherical microstructure with randomly oriented grains was aligned through the application of large-amplitude oscillatory shear (LAOS) at temperature below order–disorder transition copolymer, yet above glass polystyrene domains. The thermoplastic elastomeric behavior SAS provided convenient means to observe morphology. Following LAOS, specimen quenched room (below...
Vacuum-thermal evaporation (VTE) is a highly relevant fabrication route for organic solar cells (OSCs), especially on an industrial scale as proven by the commercialization of light emitting diode-based displays. While OSC performance reported range VTE-deposited molecules, comprehensive assessment donor:acceptor blend properties with respect to their photovoltaic scarce. Here, thin films and three select systems are fabricated ellipsometry, external quantum efficiency high dynamic range,...
Colloidal quantum dot (CQD)-based photovoltaics are an emerging low-cost solar cell technology with power conversion efficiencies exceeding 10%, i.e., high enough to be interesting for commercialization. Well-controlled and understood charge carrier transport through the device stack is required make next step in efficiency improvements. In this paper, polymer-wrapped single-walled carbon nanotube (SWNT) films embedded insulating poly(methyl methacrylate) (PMMA) matrix capped by a thermally...
The effect of a thin layer hexapropyltruxene inserted at the interface between electron donor boron subphthalocyanine chloride (SubPc) and its underlying hole contact in planar heterojunction solar cells was investigated.
Composition maps, shown within a photovoltaic device, are generated from energy-filtered transmission electron microscopy images to map out the compositional heterogeneities in active layer of polymer/fullerene solar cells with nanometer resolution. As reported by Enrique D. Gomez and coworkers article number 1400116, these help elucidate complex relationship between microstructure performance organic devices.
The electronic wave functions of an atom or molecule are affected by its interactions with environment. These dictate and optical processes at interfaces, is especially relevant in the case thin film optoelectronic devices such as organic solar cells. In these devices, charge transport interfaces between multiple layers occur along thickness vertical direction, thus different molecules---same different---are crucial determining device properties. Here, we introduce situ spectroscopic...