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Ali MA, Shoaee S, Fan S, Burn PL, Gentle IR, Meredith P, Shaw PE. Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real-Time Sensing. Chemphyschem 2016; 17:3350-3353. [PMID: 27583839 DOI: 10.1002/cphc.201600767] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Indexed: 11/09/2022]
Abstract
Time-resolved quartz crystal microbalance with in situ fluorescence measurements are used to monitor the sorption of the nitroaromatic (explosive) vapor, 2,4-dinitrotoluene (DNT) into a porous pentiptycene-containing poly(phenyleneethynylene) sensing film. Correlation of the nitroaromatic mass uptake with fluorescence quenching shows that the analyte diffusion follows the Case-II transport model, a film-swelling-limited process, in which a sharp diffusional front propagates at a constant velocity through the film. At a low vapor pressure of DNT of ≈16 ppb, the analyte concentration in the front is sufficiently high to give an average fluorophore-analyte separation of ≈1.5 nm. Hence, a long exciton diffusion length is not required for real-time sensing in the solid state. Rather the diffusion behavior of the analyte and the strength of the binding interaction between the analyte and the polymer play first-order roles in the fluorescence quenching process.
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Zarrabi N, Burn PL, Meredith P, Shaw PE. Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends. J Phys Chem Lett 2016; 7:2640-2646. [PMID: 27355877 DOI: 10.1021/acs.jpclett.6b00806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface.
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Stoltzfus DM, Donaghey JE, Armin A, Shaw PE, Burn PL, Meredith P. Charge Generation Pathways in Organic Solar Cells: Assessing the Contribution from the Electron Acceptor. Chem Rev 2016; 116:12920-12955. [DOI: 10.1021/acs.chemrev.6b00126] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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54
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Stoltzfus DM, Clulow AJ, Jin H, Burn PL, Gentle IR. Impact of Dimerization on Phase Separation and Crystallinity in Bulk Heterojunction Films Containing Non-Fullerene Acceptors. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00984] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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55
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Jansen-van Vuuren RD, Armin A, Pandey AK, Burn PL, Meredith P. Organic Photodiodes: The Future of Full Color Detection and Image Sensing. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:4766-4802. [PMID: 27111541 DOI: 10.1002/adma.201505405] [Citation(s) in RCA: 206] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 12/16/2015] [Indexed: 06/05/2023]
Abstract
Major growth in the image sensor market is largely as a result of the expansion of digital imaging into cameras, whether stand-alone or integrated within smart cellular phones or automotive vehicles. Applications in biomedicine, education, environmental monitoring, optical communications, pharmaceutics and machine vision are also driving the development of imaging technologies. Organic photodiodes (OPDs) are now being investigated for existing imaging technologies, as their properties make them interesting candidates for these applications. OPDs offer cheaper processing methods, devices that are light, flexible and compatible with large (or small) areas, and the ability to tune the photophysical and optoelectronic properties - both at a material and device level. Although the concept of OPDs has been around for some time, it is only relatively recently that significant progress has been made, with their performance now reaching the point that they are beginning to rival their inorganic counterparts in a number of performance criteria including the linear dynamic range, detectivity, and color selectivity. This review covers the progress made in the OPD field, describing their development as well as the challenges and opportunities.
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Zhou X, Burn PL, Powell BJ. Bond Fission and Non-Radiative Decay in Iridium(III) Complexes. Inorg Chem 2016; 55:5266-73. [DOI: 10.1021/acs.inorgchem.6b00219] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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57
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Abstract
Lead-based organohalide perovskites have recently emerged as arguably the most promising of all next generation thin film solar cell technologies. Power conversion efficiencies have reached 20% in less than 5 years, and their application to other optoelectronic device platforms such as photodetectors and light emitting diodes is being increasingly reported. Organohalide perovskites can be solution processed or evaporated at low temperatures to form simple thin film photojunctions, thus delivering the potential for the holy grail of high efficiency, low embedded energy, and low cost photovoltaics. The initial device-driven "perovskite fever" has more recently given way to efforts to better understand how these materials work in solar cells, and deeper elucidation of their structure-property relationships. In this Account, we focus on this element of organohalide perovskite chemistry and physics in particular examining critical electro-optical, morphological, and architectural phenomena. We first examine basic crystal and chemical structure, and how this impacts important solar-cell related properties such as the optical gap. We then turn to deeper electronic phenomena such as carrier mobilities, trap densities, and recombination dynamics, as well as examining ionic and dielectric properties and how these two types of physics impact each other. The issue of whether organohalide perovskites are predominantly nonexcitonic at room temperature is currently a matter of some debate, and we summarize the evidence for what appears to be the emerging field consensus: an exciton binding energy of order 10 meV. Having discussed the important basic chemistry and physics we turn to more device-related considerations including processing, morphology, architecture, thin film electro-optics and interfacial energetics. These phenomena directly impact solar cell performance parameters such as open circuit voltage, short circuit current density, internal and external quantum efficiency, fill factor, and ultimately the all-important power conversion efficiency. Finally, we address the key challenges pertinent to actually delivering a new and viable solar cell technology. These include long-term cell stability, scaling to the module level, and the toxicity associated with lead. Organohalide perovskites not only offer exciting possibilities for next generation optoelectronics and photovoltaics, but are an intriguing class of material crossing the boundaries of molecular solids and banded inorganic semiconductors. This is a potential area of rich new chemistry, materials science, and physics.
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Ribierre JC, Ruseckas A, Staton SV, Knights K, Cumpstey N, Burn PL, Samuel IDW. Phosphorescence quenching of fac-tris(2-phenylpyridyl)iridium(iii) complexes in thin films on dielectric surfaces. Phys Chem Chem Phys 2016; 18:3575-80. [PMID: 26750542 DOI: 10.1039/c5cp06584d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We study the influence of the film thickness on the time-resolved phosphorescence and the luminescence quantum yield of fac-tris(2-phenylpyridyl)iridium(iii) [Ir(ppy)3]-cored dendrimers deposited on dielectric substrates. A correlation is observed between the surface quenching velocity and the quenching rate by intermolecular interactions in the bulk film, which suggests that both processes are controlled by dipole-dipole interactions between Ir(ppy)3 complexes at the core of the dendrimers. It is also found that the surface quenching velocity decreases as the refractive index of the substrate is increased. This can be explained by partial screening of dipole-dipole interactions by the dielectric environment.
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Donaghey JE, Armin A, Stoltzfus DM, Burn PL, Meredith P. Correction: Dielectric constant enhancement of non-fullerene acceptors via side-chain modification. Chem Commun (Camb) 2016; 52:13714-13715. [DOI: 10.1039/c6cc90512a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Correction for ‘Dielectric constant enhancement of non-fullerene acceptors via side-chain modification’ by Jenny E. Donaghey et al., Chem. Commun., 2015, 51, 14115–14118.
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60
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Weaver LG, Singh Y, Burn PL, Blanchfield JT. The synthesis and ring-opening metathesis polymerization of glycomonomers. RSC Adv 2016. [DOI: 10.1039/c5ra25732h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The synthesis of a series of short poly(norbornene)s displaying pendant disaccharides is reported.
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Weaver LG, Singh Y, Burn PL, Blanchfield JT. Correction: The synthesis and ring-opening metathesis polymerization of glycomonomers. RSC Adv 2016. [DOI: 10.1039/c6ra90037b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Correction for ‘The synthesis and ring-opening metathesis polymerization of glycomonomers’ by Lucy G. Weaver et al., RSC Adv., 2016, 6, 31256–31264.
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Shoaee S, Fan S, Burn PL, Shaw PE. Photophysics of detection of explosive vapours via luminescence quenching of thin films: impact of inter-molecular interactions. Phys Chem Chem Phys 2016; 18:25861-25868. [DOI: 10.1039/c6cp04536g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fluorescence-based detection of explosive analytes requires an understanding of the nature of the excited state responsible for the luminescence response of a sensing material.
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63
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Ali MA, Geng Y, Cavaye H, Burn PL, Gentle IR, Meredith P, Shaw PE. Molecular versus exciton diffusion in fluorescence-based explosive vapour sensors. Chem Commun (Camb) 2015; 51:17406-9. [PMID: 26465590 DOI: 10.1039/c5cc06367a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The diffusion of p-nitrotoluene vapours into polymer or dendrimer sensing films follows Super Case II dynamics in which the quenching efficiency is strongly correlated to an accelerating analyte front propagating through the neat film rather than being reliant on exciton diffusion.
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Clulow AJ, Gilbert EP, Wolfer P, Burn PL, Gentle IR. Clustering of High Molecular Weight PCDTBT in Bulk-Heterojunction Casting Solutions. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b02040] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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65
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Donaghey JE, Armin A, Burn PL, Meredith P. Dielectric constant enhancement of non-fullerene acceptors via side-chain modification. Chem Commun (Camb) 2015; 51:14115-8. [PMID: 26255993 DOI: 10.1039/c5cc05853h] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The low dielectric constants of conventional organic semiconductors leads to poor charge carrier photogeneration in homojunction organic solar cells due to large exciton binding energies. Increasing the dielectric constant can potentially enhance the spontaneous exciton dissociation rate at room temperature in homojunction cells, and decrease the charge carrier recombination in heterojunction solar cells comprising blends of electron donors and acceptors. We report that substituting the ubiquitous alkyl solubilizing groups with short glycol chains can give non-fullerene electron acceptors with a static dielectric constant of up to 9.8.
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Muhieddine K, Ullah M, Maasoumi F, Burn PL, Namdas EB. Hybrid Area-Emitting Transistors: Solution Processable and with High Aperture Ratios. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:6677-6682. [PMID: 26400042 DOI: 10.1002/adma.201502554] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/23/2015] [Indexed: 06/05/2023]
Abstract
Area emission is realized in all-solution-processed hybrid light-emitting transistors (HLETs). A new HLET design is presented with increased aperture ratio, and optical and electrical characteristics are shown.
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67
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Liew JY, Lo SC, Burn PL, Krausz ER, Hall JD, Moore EG, Riley MJ. Analysis of the emitting states of an Ir(III) complex with strong blue emission. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.10.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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68
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Gonzalez-Vazquez JP, Burn PL, Powell BJ. Interplay of Zero-Field Splitting and Excited State Geometry Relaxation in fac-Ir(ppy)3. Inorg Chem 2015; 54:10457-61. [DOI: 10.1021/acs.inorgchem.5b01918] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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69
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Geng Y, Ali MA, Clulow AJ, Fan S, Burn PL, Gentle IR, Meredith P, Shaw PE. Unambiguous detection of nitrated explosive vapours by fluorescence quenching of dendrimer films. Nat Commun 2015; 6:8240. [PMID: 26370931 PMCID: PMC4579782 DOI: 10.1038/ncomms9240] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Accepted: 07/31/2015] [Indexed: 12/11/2022] Open
Abstract
Unambiguous and selective standoff (non-contact) infield detection of nitro-containing explosives and taggants is an important goal but difficult to achieve with standard analytical techniques. Oxidative fluorescence quenching is emerging as a high sensitivity method for detecting such materials but is prone to false positives—everyday items such as perfumes elicit similar responses. Here we report thin films of light-emitting dendrimers that detect vapours of explosives and taggants selectively—fluorescence quenching is not observed for a range of common interferents. Using a combination of neutron reflectometry, quartz crystal microbalance and photophysical measurements we show that the origin of the selectivity is primarily electronic and not the diffusion kinetics of the analyte or its distribution in the film. The results are a major advance in the development of sensing materials for the standoff detection of nitro-based explosive vapours, and deliver significant insights into the physical processes that govern the sensing efficacy. Selective standoff detection of explosives is challenging due to the presence of volatile interferents. Here, the authors report dendrimer thin films that display distinct fluorescence responses when exposed to explosives as opposed to common interferents, allowing selective detection of nitrated explosives.
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Stolterfoht M, Armin A, Philippa B, White RD, Burn PL, Meredith P, Juška G, Pivrikas A. Photocarrier drift distance in organic solar cells and photodetectors. Sci Rep 2015; 5:9949. [PMID: 25919439 PMCID: PMC4412075 DOI: 10.1038/srep09949] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 03/23/2015] [Indexed: 11/09/2022] Open
Abstract
Light harvesting systems based upon disordered materials are not only widespread in nature, but are also increasingly prevalent in solar cells and photodetectors. Examples include organic semiconductors, which typically possess low charge carrier mobilities and Langevin-type recombination dynamics--both of which negatively impact the device performance. It is accepted wisdom that the "drift distance" (i.e., the distance a photocarrier drifts before recombination) is defined by the mobility-lifetime product in solar cells. We demonstrate that this traditional figure of merit is inadequate for describing the charge transport physics of organic light harvesting systems. It is experimentally shown that the onset of the photocarrier recombination is determined by the electrode charge and we propose the mobility-recombination coefficient product as an alternative figure of merit. The implications of these findings are relevant to a wide range of light harvesting systems and will necessitate a rethink of the critical parameters of charge transport.
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71
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Stapleton AJ, Yambem SD, Johns AH, Afre RA, Ellis AV, Shapter JG, Andersson GG, Quinton JS, Burn PL, Meredith P, Lewis DA. Planar silver nanowire, carbon nanotube and PEDOT:PSS nanocomposite transparent electrodes. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2015; 16:025002. [PMID: 27877771 PMCID: PMC5036479 DOI: 10.1088/1468-6996/16/2/025002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 01/13/2015] [Indexed: 05/30/2023]
Abstract
Highly conductive, transparent and flexible planar electrodes were fabricated using interwoven silver nanowires and single-walled carbon nanotubes (AgNW:SWCNT) in a PEDOT:PSS matrix via an epoxy transfer method from a silicon template. The planar electrodes achieved a sheet resistance of 6.6 ± 0.0 Ω/□ and an average transmission of 86% between 400 and 800 nm. A high figure of merit of 367 Ω-1 is reported for the electrodes, which is much higher than that measured for indium tin oxide and reported for other AgNW composites. The AgNW:SWCNT:PEDOT:PSS electrode was used to fabricate low temperature (annealing free) devices demonstrating their potential to function with a range of organic semiconducting polymer:fullerene bulk heterojunction blend systems.
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72
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Lin Q, Armin A, Lyons DM, Burn PL, Meredith P. Low noise, IR-blind organohalide perovskite photodiodes for visible light detection and imaging. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:2060-2064. [PMID: 25677496 DOI: 10.1002/adma.201405171] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 12/14/2014] [Indexed: 06/04/2023]
Abstract
Solution-processed organohalide perov-skite photodiodes that have performance metrics matching silicon, but are infrared-blind are reported. The perovskite photodiodes operate in the visible band, have low dark current and noise, high specific detectivity, large linear dynamic range, and fast temporal response. Their properties make them promising candidates for imaging applications.
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73
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Ullah M, Armin A, Tandy K, Yambem SD, Burn PL, Meredith P, Namdas EB. Defining the light emitting area for displays in the unipolar regime of highly efficient light emitting transistors. Sci Rep 2015; 5:8818. [PMID: 25743444 PMCID: PMC4351517 DOI: 10.1038/srep08818] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 01/26/2015] [Indexed: 11/25/2022] Open
Abstract
Light-emitting field effect transistors (LEFETs) are an emerging class of multifunctional optoelectronic devices. It combines the light emitting function of an OLED with the switching function of a transistor in a single device architecture. The dual functionality of LEFETs has the potential applications in active matrix displays. However, the key problem of existing LEFETs thus far has been their low EQEs at high brightness, poor ON/OFF and poorly defined light emitting area - a thin emissive zone at the edge of the electrodes. Here we report heterostructure LEFETs based on solution processed unipolar charge transport and an emissive polymer that have an EQE of up to 1% at a brightness of 1350 cd/m2, ON/OFF ratio > 104 and a well-defined light emitting zone suitable for display pixel design. We show that a non-planar hole-injecting electrode combined with a semi-transparent electron-injecting electrode enables to achieve high EQE at high brightness and high ON/OFF ratio. Furthermore, we demonstrate that heterostructure LEFETs have a better frequency response (fcut-off = 2.6 kHz) compared to single layer LEFETs. The results presented here therefore are a major step along the pathway towards the realization of LEFETs for display applications.
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Armin A, Jansen-van Vuuren RD, Kopidakis N, Burn PL, Meredith P. Narrowband light detection via internal quantum efficiency manipulation of organic photodiodes. Nat Commun 2015; 6:6343. [DOI: 10.1038/ncomms7343] [Citation(s) in RCA: 332] [Impact Index Per Article: 36.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 01/21/2015] [Indexed: 01/23/2023] Open
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75
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Fang Y, Pandey AK, Lyons DM, Shaw PE, Watkins SE, Burn PL, Lo SC, Meredith P. Tuning the Optoelectronic Properties of Nonfullerene Electron Acceptors. Chemphyschem 2014; 16:1295-304. [PMID: 25335767 DOI: 10.1002/cphc.201402568] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Indexed: 11/06/2022]
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