A5010409040- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Molecular Junctions and Nanostructures
- Perovskite Materials and Applications
- Thin-Film Transistor Technologies
- Organic Light-Emitting Diodes Research
- Semiconductor materials and interfaces
- X-ray Diffraction in Crystallography
- Fullerene Chemistry and Applications
- Silicon and Solar Cell Technologies
- Photochemistry and Electron Transfer Studies
- Crystallization and Solubility Studies
- Analytical Chemistry and Sensors
- Advanced Electron Microscopy Techniques and Applications
- Advanced Photocatalysis Techniques
- Neuroscience and Neural Engineering
- Photovoltaic System Optimization Techniques
- Chalcogenide Semiconductor Thin Films
- Advanced Fluorescence Microscopy Techniques
- Quantum Dots Synthesis And Properties
- Crystallography and molecular interactions
- Gas Sensing Nanomaterials and Sensors
- Organic Chemistry Cycloaddition Reactions
- Photoreceptor and optogenetics research
Imperial College London
2015-2024
Plastic Electronics (Netherlands)
2019
Kensington Health
2018
Transnational Press London
2014-2018
Swansea University
2014
We report the synthesis and polymerization of a novel thieno[3,2-b]thiophene−diketopyrrolopyrrole-based monomer. Copolymerization with thiophene afforded polymer maximum hole mobility 1.95 cm2 V−1 s−1, which is highest from polymer-based OFET reported to date. Bulk-heterojunction solar cells comprising this PC71BM gave power conversion efficiency 5.4%.
Ideality factors are derived from either the slope of dark current/voltage curve or light intensity dependence open-circuit voltage in solar cells and often a valuable method to characterize type recombination. In case polymer:fullerene cells, ideality by two methods usually differ substantially. Here we investigate reasons for discrepancies determining both differentially as function comparing them with simulations. We find that sensitive bulk recombination mechanisms at internal...
Abstract Photoinduced charge separation in bulk heterojunction solar cells is studied using a series of thiazolo‐thiazole donor polymers that differ their side groups (and bridging atoms) blended with two acceptor fullerenes, phenyl‐C 71 ‐butyric acid methyl ester (PC BM) and fullerene indene‐C60 bisadduct (ICBA). Transient absorption spectroscopy used to determine the yields lifetimes photogenerated carriers, complimented by cyclic voltammetry studies materials energetics, wide angle X‐ray...
Minimizing the energy offset between lowest exciton and charge-transfer (CT) states is a widely employed strategy to suppress loss (Eg/q – VOC) in polymer:non-fullerene acceptor (NFA) organic solar cells (OSCs). In this work, transient absorption spectroscopy determine CT state lifetimes series of low polymer:NFA blends. The lifetime observed show an inverse gap law dependence decreases as reduced. This behavior assigned increased mixing/hybridization these shorter-lived singlet excitons...
Abstract We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon layer thickness. These and devices are analysed by transient optoelectronic techniques carrier kinetics densities, air photoemission spectroscopy material energetics, Kelvin probe measurements work function, Mott-Schottky analyses apparent doping density device modelling. conclude that, for the series studied, photocurrent loss thick active layers is...
Electron spin is a key consideration for the function of organic semiconductors in light-emitting diodes and solar cells, as well spintronic applications relying on magnetoresistance. A mechanism triplet excited state generation such systems by recombination electron-hole pairs. However, exact charge mechanism, whether geminate or nongeminate it involves spin-state mixing not understood. In this work, dynamics free separation competing with to polymer states studied two closely related...
Abstract The synthesis and characterization four diketopyrrolopyrrole containing conjugated polymers for use in organic photovoltaics is presented. Excellent energy level control demonstrated through heteroatomic substitution whilst maintaining similar solid state properties as shown by X‐ray diffraction atomic force microscopy. Inverted solar cells were fabricated with the best devices having short circuit currents exceeding 16 mA cm −2 efficiencies of over 5% irrespective whether...
Energetic disorder in organic semiconductors leads to strong dependence of recombination kinetics and mobility on charge density. However, observed mobilities reaction orders are normally interpreted assuming uniform carrier distributions. In this paper, we explore the effect spatial distribution determination rate as a function average Since gradient changes when thickness device is varied, study series two different polymer:fullerene systems measure density lifetime. Using simulations, can...
We present the synthesis and characterization of two novel thiazole-containing conjugated polymers (PTTTz PTTz) that are isostructural to poly(3-hexylthiophene) (P3HT). The materials demonstrate optical morphological properties almost identical those P3HT but with HOMO LUMO levels up 0.45 eV deeper. An intramolecular planarizing nitrogen–sulfur nonbonding interaction is observed, its magnitude origin discussed. Both significantly greater open circuit voltages than in bulk heterojunction...
Thieno[3,2-b]thienobis(silolothiophene), a new electron rich hexacyclic monomer has been synthesized and incorporated into three novel donor–acceptor low-bandgap polymers. By carefully choosing the acceptor co-monomer, energy levels of polymers could be modulated high power conversion efficiencies 5.52% were reached in OPV devices.
Herein, a new ternary strategy to fabricate efficient and photostable inverted organic photovoltaics (OPVs) is introduced by combining bulk heterojunction (BHJ) blend fullerene self-assembled monolayer (C
The role of PC70BM excitons in driving charge photogeneration low bandgap polymer/fullerene bulk heterojunction solar cells has been studied. Both transient absorption spectroscopy generation yields blend films as a function excitation energies and photocurrent quantum efficiency spectra the corresponding devices indicate that this system results primarily from direct optical PC70BM. Blend composition studies density photoluminescence quenching is determined by limited exciton diffusion to...
Despite performance improvements of organic photovoltaics, the mechanism photoinduced electron–hole separation at donor–acceptor interfaces remains poorly understood. Inconclusive experimental and theoretical results have produced contradictory models for in which role interfacial charge-transfer (CT) states is unclear, with one model identifying them as limiting another readily dissociating. Here, polymer–fullerene blends contrasting photocurrent properties enthalpic offsets driving were...
Recent progress in organic photovoltaics (OPVs) has been enabled by optimization of the energetic driving force for charge separation, and thus maximization open-circuit voltage, using non-fullerene acceptor (NFA) materials. In spite this, carrier dynamics relative energies key states controlling photophysics these systems are still under debate. Herein, we report an in-depth ultrafast spectroscopic study a representative OPV system based on polymer donor PffBT4T-2OD small-molecule NFA...
Additive engineering is emerging as a powerful strategy to further enhance the performance of perovskite solar cells (PSCs), with incorporation bulky cations and amino acid (AA) derivatives being shown promising for enhanced device stability. However, such additives typically results in photocurrent losses owing their saturated carbon backbones, hindering charge transport collection. Here, we investigate use AAs varying chain lengths zwitterionic PSC stability, air nitrogen, under...
Abstract Single‐component organic solar cells based on double cable polymers have achieved remarkable performance, with DCPY2 reaching a high efficiency of over 13%. In this study, is further optimized an 13.85%, maintaining fill factor (FF) without compromising the short circuit current. Despite its intermixed morphology, shows reduced recombination rate compared to their binary counterpart (PBDB‐T:Y‐O6). This slower in attributed wavefunction overlap delocalized charges, by spatially...
We report a comparison of charge carrier dynamics and device performance for low band gap polymer PBDTTT-CT in blends with the fullerene acceptor PC71BM PDI derivative similar electron affinities. Charge separation recombination are found to be remarkably these two acceptors, both exhibiting efficient, ultrafast (time constants 1.6 1.4 ps, respectively). The lower (1.75% compared 3.5% equivalent device) is shown result from slower transport, increasing nongeminate losses during collection.
The effects of climate change can be mitigated by developing alternative energy sources. An investigation shows how the performance organic solar cells degrades for doping levels above $7\ifmmode\times\else\texttimes\fi{}{10}^{15}$ cm${}^{-3}$.
A new synthetic route to the electron accepting di-cyano substituted benzo[<italic>d</italic>][1,2,3]triazole (BTz) monomer 2-(2-butyloctyl)-4,7-di(thiophen-2-yl)-2<italic>H</italic>-benzotriazole-5,6-dicarbonitrile (<bold>dTdCNBTz</bold>) is reported.
The performance of bulk heterojunction solar cells based on a novel donor polymer DPP-TT-T was optimised by tuning molecular weight and thermal annealing.
In this work we lay out design guidelines for catalytically more efficient organic photocathodes achieving stable hydrogen production in neutral pH. We propose an photocathode architecture employing a NiO hole selective layer, PCDTBT:PCBM bulk heterojunction, compact TiO2 electron contact and RuO2 nanoparticle catalyst. The role of each layer is discussed terms durability function. With strategically designed obtain photocurrent densities over 5 h discuss routes further performance improvement.
We explore the effect of moving well-known thiadiazole unit away from polymer backbone on optoelectronic properties and ultimately device performance.
A key challenge in achieving control over photocurrent generation by bulk-heterojunction organic solar cells is understanding how the morphology of active layer impacts charge separation and particular dynamics within molecularly intermixed donor–acceptor domains versus between phase-segregated domains. This paper addresses this issue studying blends devices amorphous silicon–indacenodithiophene polymer SiIDT-DTBT acceptor PC70BM. By changing blend composition, we modulate size density pure...
Abstract Fundamental mechanisms underlying exciton formation in organic semiconductors are complex and elusive as it occurs on ultrashort sub-100-fs timescales. Some fundamental aspects of this process, such the evolution binding energy, have not been resolved time experimentally. Here, we apply a combination sub-10-fs Pump-Push-Photocurrent, Pump-Push-Photoluminescence, Pump-Probe spectroscopies to polyfluorene devices track ultrafast excitons. While is sensitive total concentration excited...
Soluble co-polymers of the fused selenophene monomer, DSG, with<italic>N</italic>-octylthienopyrrolodione are reported. Polymer solar cells fabricated from blends with PC<sub>71</sub>BM exhibit promising performance in inverted bulk heterojunction