Search query: single quantum dot Enhanced Energy Transfer

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abstract: Singlet fission (SF) an exciton multiplication process occurring in organic semiconductors, offers a way to break the Shockley Queisser limit in single bandgap photovoltaics (PV) If the triplet excitons generated by SF can be transferred to inorganic quantum dots (QDs) where they radiatively recombine, SF based photon multiplication is achieved, converting a single high energy photon into two low energy photons. Such a SF photon multiplication film (SF PMF) could raise the efficiency of the best Si PV from 26.7% to 32.5% But a precise nanoscale morphology is required within such a film consisting of the appropriate morphology for the organic phase, allowing for efficient SF, within which the QD emitters are well dispersed on a tens of nm length scale to enable efficient harvesting of the triplets. However, it has been a long standing problem that the individual components in organic QD blends have a tendency to aggregate and phase separate, due to a mismatch of their size, shape and surface energies. Here, we demonstrate a QD surface engineering approach using an electronically active, highly soluble semiconductor ligand that is matched to the SF material, which allows us to direct the self assembly process yielding solution processed films with well dispersed QDs and minimal aggregation, as characterised by X ray and neutron scattering and electron microscopy. Steady state and time resolved optical spectroscopy show that the films support efficient SF (190% yield) in the organic phase and quantitative triplet energy transfer across the organic QD interface, resulting in 95% of the triplet excitons being harvested by the QDs. Our results establish the SF PMF as a highly promising architecture to harness the SF process to enhance PV efficiencies, and also provide a highly versatile approach to overcome challenges in the blending of organic semiconductors with QDs.
author_names: Jesse R Allardice

Victor Gray

Simon A Dowland

Daniel T W Toolan

Michael P Weir

James Xiao

Zhilong Zhang

Jurjen F Winkel

Anthony J Petty

John E Anthony

Richard H Friend

Anthony J Ryan

Richard A L Jones

Neil C Greenham

Akshay Rao
title: Ligand Directed Self Assembly of Bulk Organic Semiconductor/Quantum Dot Blend Films Enables Near Quantitative Harvesting of Triplet Excitons
year: 2020

abstract: In this work we provide numerical results concerning an all optical inhibitory integrate and fire neuron based on a single section quantum dot InAs/GaAs laser. The numerical model employs a detailed multi population approach that accommodates electron hole dynamics and can efficiently describe waveband transitions from both the ground and excited energy state. The underlying physical mechanism of waveband switching in an inhibitory neuron is unveiled and is attributed to hole electron's transport time asymmetries. A detailed dynamical analysis allowed the identification of suitable optical injection regimes so as to trigger highly sought neuro computational behaviors such as rate encoding and neural spikes with picosecond temporal resolution.
author_names: George Sarantoglou

Menelaos Skontranis

Charis Mesaritakis
title: All Optical Integrate and Fire Neuromorphic Node Based on Single Section Quantum Dot Laser
venue: IEEE Journal of Selected Topics in Quantum Electronics
year: 2020

abstract: The influence of meso tetra(3 pyridyl)porphyrin (TPyP) on Forster resonance energy transfer (FRET) in aggregates of CdSe colloidal quantum dots (CQDs) has been studied. Upon the formation of such aggregates, interparticle FRET arises, leading to two effects. First, due to blinking, the observed luminescence quantum yield decreases. Second, due to inhomogeneous broadening of the optical spectra of CQDs, the luminescence band shifts to the long wavelength side. The introduction of TPyP into the system leads to its adsorption on CQDs with multi timescale kinetics. As a result, FRET from CQDs to TPyP arises, which effectively competes with FRET between CQDs themselves. As a result, the red shift arising due to aggregation of CQDs is significantly reduced. In this case, the dye adsorption has no effect on the position of the luminescence peak of the non aggregated particles.
author_names: L M Nikolenko

A V Gadomskaya

Maxim G Spirin

Sergey A Tovstun

Sergei B Brichkin

Vladimir F Razumov
title: Forster Resonance Energy Transfer in Aggregates of CdSe Colloidal Quantum Dots with Adsorbed meso Tetra(3 pyridyl)porphyrin
venue: High Energy Chemistry
year: 2020

abstract: Colloidal perovskite quantum dots are candidate materials for solution processable lasers, although stimulated emission in a semiconductor usually occurs in the multiexciton regime. Due to the quantum confinement effect of semiconductor quantum dots, the non radiative recombination transition dominates the relaxation of multiexcitons. Hence, the implementation of low threshold stimulated emission of perovskite quantum dots in the single exciton regime is meaningful. Herein, we show that this problem can be partially solved by employing a locally enhanced electric field. By applying the metal surface plasmon resonance energy transfer effect, we demonstrate a considerable reduction of the optical gain threshold due to the newly generated coupling level induced by the local surface plasmon, and obtain optical gain in the single exciton regime at room temperature in colloidal perovskite quantum dots. At the same time, we achieve a more than fourfold reduction in the amplified spontaneous emission threshold. This may provide a new concept for the further design of low threshold stimulated emission colloidal nanocrystal lasers and even for improving their energy conversion efficiency.
author_names: Litao Zhao

Yi-Hsien Chen

Xiantong Yu

Xiao Xing

Jinquan Chen

Jun Song

Junle Qu
title: Low threshold stimulated emission in perovskite quantum dots: single exciton optical gain induced by surface plasmon polaritons at room temperature
year: 2020

abstract: Ability to create high contrast multicolor luminescent patterns is essential to realize the full potential of quantum dots (QDs) in display technologies. The idea of using a non emissive state is adopted in the present work to enhance the color contrast of QD based photopatterns. This is achieved at a multicolor level by the photoregulation of electron and energy transfer processes in a single QD nanohybrid film, comprising of one QD donor and two dye acceptors. The dominance of photoinduced electron transfer over energy transfer process generates a non luminescent QD nanohybrid film, which provides the black background for multicolor patterning. The superior photostability of QDs over dyes is used for the photoregulation of electron and energy transfer processes. Selective photodegradation of electron acceptor dye triggered the onset of energy transfer process, thereby imparting a luminescent color to QD nanohybrid film. Further, a controlled photoregulation of energy transfer process paved the way for multicolor patterning.
author_names: Gayathri Devatha

Pradyut Roy

Anish Rao

Soumendu Shekhar Roy

Pramod P Pillai
title: Multicolor Luminescent Patterning via Photoregulation of Electron and Energy Transfer Processes in Quantum Dots.
venue: The journal of physical chemistry letters
year: 2020

abstract: This thesis presents work on a series of devices for the generation of photonic quantum states based on self assembled InAs quantum dots, which are among the most technologically mature candidates for practical quantum photonic applications due to their high internal quantum efficiency, narrow linewidth, tunability and straightforward integration with photonic and electric components. The primary results presented concern sources of multi photon entangled states and single photon sources with high repetition rate, both of which are crucial components for emerging photonic quantum technologies. First, we propose a scheme for the sequential generation of entangled photon chains by resonant scattering of a laser field on a single charged particle in a cavity enhanced quantum dot. The charge has an associated spin that can determine the time bin of a photon, allowing for information encoding in this degree of freedom. We demonstrate coherent operations on this spin and realize a proof of principle experiment of the proposed scheme by showing that the time bin of a single photon is dependent on the measured state of the trapped spin. The second main avenue of work investigates the effects of a surface acoustic wave, a mechanical displacement wave confined to the surface of a substrate, on the optical properties of quantum dots. In particular, we exploit the dynamic acoustically induced tuning of the emission energy to modulate the Purcell effect in a pillar microcavity. Under resonant optical excitation we demonstrate the conversion of the continuous wave laser into a pulsed single photon stream inheriting the acoustic frequency of 1 GHz as the repetition rate. High resolution spectroscopy reveals the presence of narrow sidebands in the emission spectrum, whose relative intensity can be controlled by the acoustic power and laser detuning. Furthermore, we develop a platform for analogous in plane experiments by transferring GaAs membranes hosting quantum dots onto LiNbO3 substrates and patterning them into whispering gallery mode optical resonators. In addition to Purcell enhancement and acoustic tuning of the emission, the devices exhibit strong localized mechanical resonances. Finally, we perform initial experiments on the effects of a surface acoustic wave on the spin of a charge trapped in a quantum dot. We integrate acoustic transducers with charge tunable diodes, where the charge state of the dot can be precisely controlled by an applied bias voltage, and demonstrate the frustration of optical spin pumping by the acoustic wave. List of Publications Villa B. Bennett A. J. Ellis D. J. P. Lee J. P. Skiba Szymanska J. Mitchell T. A. Griffiths J. P. Farrer I. Ritchie D. A. Ford C.J.B. Shields A. J. Surface Acoustic Wave Modulation of a Coherently Driven Quantum Dot in a Pillar Microcavity. Applied Physics Letters 111, 011103 2017 Lee J.P. Villa B. Bennett A. J. Stevenson R. M. Ellis D. J. P. Farrer I. Ritchie D. A. Shields A. J. A Quantum Dot as a Source of Time Bin Entangled Multi Photon States. Quantum Science and Technology 4, 025011 2019 Lee J.P. Wells L.M. Villa B. Kalliakos S. Stevenson R.M. Ellis D.J.P. Farrer I. Ritchie D. A. Bennett, A. J. Shields A. J. Controllable Photonic Time Bin Qubits from a Quantum Dot. Phys. Rev. X. 8, 021078 2018 Wells L.M. Kalliakos S. Villa B. Ellis D.J.P. Stevenson R.M. Bennett A.J. Farrer I. Ritchie D.A. Shields A.J. Photon Phase Shift at the Few Photon Level and Optical Switching by a Quantum Dot in a Microcavity. Phys. Rev. Applied 11, 061001 2019
author_names: Bruno Villa Pineros
title: Dynamic acoustic control of semiconductor quantum dot based devices for quantum light generation
year: 2020

abstract: Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy tailored system via Forster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two dimensional CsPbBr3 based nanoplatelets (NPls) In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRET mediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to kFRET 0.99 ns 1 and efficiencies of nearly eFRET 70% We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored energy cascade nanostructures for improved optoelectronic devices.
author_names: Andreas Singldinger

Moritz Gramlich

Christoph Gruber

Carola Lampe

Alexander S Urban
title: Nonradiative Energy Transfer between Thickness Controlled Halide Perovskite Nanoplatelets
venue: ACS energy letters
year: 2020

abstract: A molecularly imprinted magnetic sensor with electroluminescent tags (MIP ECL sensor) was developed for ultrasensing diethylstilbestrol (DES) A strategy is exploited to enhance ECL emission of the [Ru(bpy)3]2 tripropyl amine (TPrA) system by CdTe@ZnS quantum dots (QDs) through energy transfer. Magnetically molecularly imprinted nanoparticles (MMIPs NPs) based on Fe3O4@SiO2 carriers are artificial, easily reproducible, and could replace easily inactivated first antibodies for capturing more DES molecules. Functionalized bio conjugates of single antibody CdTe@ZnS (Ab CdTe@ZnS) are for the first time loaded on signal labels of Ru(bpy)32 doped silica nanocomposites (Ru@SiO2) for signal amplification. The final bio conjugated signal probes are denoted as Ab DES/CdTe@ZnS Ru@SiO2. MMIPs beads that have captured antigens are bio conjugated with antibody labeled luminescent probes by specific immunoreactive reaction, and then the luminescent immunocomplex generates ECL signal on the magnetic electrode. The logarithm of ECL intensities depend linearly on the logarithm of DES concentrations in the range from 4.8 x 10 4 to 36.0 nM with a detection limit of 0.025 pM. This novel assay is much more sensitive than other MIP sensors, and achieves lower cost and more enhanced stability than other immunosensors. The sensor is significantly potential and has been applied to DES detection in actual environment.
author_names: Wenru Zhao

Yaohua Xu

Tian-fang Kang

Xiao Hang Zhang

Huicong Liu

Anjie Ming

Shuiyuan Cheng

Fengwei Wei
title: Sandwich magnetically imprinted immunosensor for electrochemiluminescence ultrasensing diethylstilbestrol based on enhanced luminescence of Ru@SiO2 by CdTe@ZnS quantum dots.
venue: Biosensors bioelectronics
year: 2020

abstract: CpG island methylation plays an important role in diverse biological processes including the regulation of imprinted genes, X chromosome inactivation, and tumor suppressor gene silencing in human cancer. Due to the dependence of DNA methylation on DNA methyltransferase (MTase) activity, DNA MTases have become the potential targets in anticancer therapy. Herein we demonstrate for the first time the construction of a single quantum dot (QD) nanosensor with the capability of sensing methylcytosine sites for sensitive quantification of M.SssI CpG methyltransferase (M.SssI MTase) We design a biotin /phosphate modified double stranded DNA (dsDNA) substrate with a 5' G C G mC 3'/3' mC G mC G 5' site for sensing M.SssI MTase. In the presence of M.SssI MTase, the methylation responsive sequence of the dsDNA substrate is methylated and cleaved by GlaI endonuclease, producing two dsDNA fragments with a free 3' OH terminus. In the presence of terminal deoxynucleotidyl transferase (TdT) multiple Cy5 dATPs can be sequentially added to the free 3' OH terminus of dsDNA fragments to obtain biotin /multiple Cy5 labeled dsDNAs. The resultant biotin /multiple Cy5 labeled dsDNAs can assemble on the surface of the streptavidin coated QD to obtain a QD dsDNA Cy5 nanostructure in which the fluorescence resonance energy transfer (FRET) from the QD to Cy5 can occur. The emission of Cy5 can be simply quantified by single molecule detection. By the integration of sensing methylcytosine sites and enzymatic polymerization, the sensitivity of this nanosensor has been significantly enhanced. This nanosensor can detect as low as 2.1 x 10 7 U mL 1 M.SssI MTase with good selectivity against other cytosine MTases, and it can be further applied for the screening of MTase inhibitors and complex biological sample analysis, holding great potential in clinical diagnosis and drug discovery.
author_names: Juan Hu

Yuting Liu

Chun-yang Zhang
title: Construction of a single quantum dot nanosensor with the capability of sensing methylcytosine sites for sensitive quantification of methyltransferase.
venue: Nanoscale
year: 2020

abstract: Abstract Highly efficient, all solution processed inverted quantum dot light emitting diodes (QLEDs) with high performance are demonstrated by employing poly(9 vinlycarbazole) (PVK) as additional hole transport layer (HTL) and doping it with a blue thermal activated delay fluorescent (TADF) material, 4,5 bis(carbazol 9 yl) 1,2 dicyanobenzene (2CzPN) This PVK: 2CzPN composite layer not only optimizes hole injection, but also utilizes the leaked electrons to enhance device luminance by energy transfer process from 2CzPN to quantum dots (QDs) These benefits enable a 20 fold increment for the device current efficiency (from 0.523 cd/A to 11 cd/A) and a 9.9 fold improvement for the maximum luminance (from 3220 cd/m2 to 35352 cd/m2) compared with those of the standard QLED with poly[(9, 9 dioctylfluorenyl 2,7 diyl) alt (4,4' (N (4 butylphenyl) (TFB) single HTL. In comparison with the QLED with TFB/pristine PVK double HTLs, the device performance of the optimal QLED with PVK: 2CzPN additional HTL are still 40.8% and 61.7% higher in luminance and current efficiency, respectively.
author_names: Weiye Zheng

Dan-dan Song

Suling Zhao

Bo Qiao

Zhaopeng Xu

Junfei Chen

Pingshan Wang

Yue Liang
title: All solution processed inverted QLEDs with double hole transport layers and thermal activated delay fluorescent dopant as energy transfer medium
year: 2020