We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO layer: a flat ZnO backing layer alone; vertically aligned ZnO nanorods on a ZnO backing layer; and ZnO nanoparticles on a ZnO backing layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition of the P3HT polymer yields a power conversion efficiency over four times greater than that for a similar device based on the nanoparticle structure. The best ZnO nanorod:P3HT device yields a short circuit current density of 2 mAcm(-2) under AM1.5 illumination (100 mW cm(-2)) and a peak external quantum efficiency over 14%, resulting in a power conversion efficiency of 0.20%.

Nanorod

Active layer

10.1021/jp0571372

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Citations (541)

4H-1,2,6-Thiadiazin-4-one-containing small molecule donors and additive effects on their performance in solution-processed organic solar cells

Journal of Materials Chemistry C (2015)

Felix Hermerschmidt Andreas S. Kalogirou Jie Min Georgia A. Zissimou Sachetan M. Tuladhar

Donor–acceptor–donors containing 4H-1,2,6-thiadiazinone are presented and used in organic solar cells.

Acceptor

Organic molecules

10.1039/c4tc02931c

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Citations (29)

Power and beam characteristics of semiconducting polymer lasers pumped by a microchip laser

Graham A. Turnbull Piers Andrew G. Heliotis Ran Xia William L. Barnes

They exhibit strong absorption hands with peak absorption coefficients -10’ cm?, and large optical gain cross-sections cm’, giving the possibility of enormous gain. Emission bandwidths can exceed 100 nm, and may be tuned from 400 to 700 nm by appropriate chemical design. Unlike small dye molecules, polymers exhibit little concentration quenching, and show fluorescence quantum efficiencies as high as 60% in the undiluted solid state. Particularly important is their capacity for simple processing. Both solution processing, and hot embossing. can be used to form flexible shapes and structures that may control the light emission. To date, polymer lasers have used large-frame laser systems (e.g. Tisapphire and nitrogen lasers) for excitation [1,2]. We now report improved polymer lasers that are pumped by a small microchip laser. In doing so, we have formed compact and convenient all-solid-state laser systems with the potential for broad spectral tuning. Specifically, we report blue and red lasing at wavelengths around 460, 635 and 675 nm from surface-emitting, distributed feedback lasers using the conjugated polymer MEHPPV, and several polyfluorene derivatives. We present the output energy, efficiency and spectral characteristics of the devices, and a detailed analysis of the surface-emitted laser modes.

Polyfluorene

Gain-switching

10.1109/cleoe.2003.1313432

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Measuring the Efficiency of Organic Light‐Emitting Devices

Advanced Materials (2003)

Stephen R. Forrest Donal D. C. Bradley Mark E. Thompson

As organic light‐emitting devices emerge from the stage of being a research curiosity to that of becoming a practical appliance with important commercial applications, the need for a coherent and accurate standard technique for measuring device efficiencies becomes increasingly important. By following the methods described in this contribution, measurements made in disparate laboratories testing a wide range of materials and device structures should agree, to within small experimental errors, on the properties of the subject devices.

Curiosity

10.1002/adma.200302151

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Citations (560)

Low-threshold lasers based on a high-mobility semiconducting polymer

Applied Physics Letters (2006)

G. Heliotis Stelios A. Choulis Grigorios Itskos Ruidong Xia R. Murray

Progress toward electrically driven conjugated polymer lasers should benefit from the identification of materials that exhibit good charge transport properties coupled with large optical gain. Here, we report a detailed study of a blue-emitting fluorene-based polymer that combines a large hole mobility with desirable stimulated emission characteristics. Laser oscillation is achieved within distributed feedback structures and leads to low threshold, tunable lasers operating in the blue spectral region. Our results establish this material as an attractive gain medium with which to try and construct a polymer laser diode.

Oscillation (cell signaling)

Electron Mobility

Amplified spontaneous emission

10.1063/1.2178197

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Citations (23)

Comparison between bulk and field effect mobility in polyfluorene copolymer field effect transistors

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2003)

Ruth Rawcliffe Donal D. C. Bradley Alasdair J. Campbell

Polymer field-effect-transistors (FETs) have been proposed for use in display driver circuitry, information storage and processing, and identity tags. To maximize performance in polymer FETs it is important to have a high carrier mobility. A major issue in this area is how the FET mobility, as measured by analysis of source-drain current-voltage characteristics, relates to the bulk mobility, as measured by a technique such as the time-of-flight (TOF) photocurrent or space-charge-limited current (SCLC) methods. Here we report comparative FET, TOF and SCLC measurements of polyfluorene copolymer devices. Poly (9,9-dioctylfluorene-co-bithiophene) (F8T2) and poly (9,9-dioctylfluorene-co-bis-N, N'-(4 butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) were used as the active material. Polymer FETs were fabricated in two different structures. The first involved a silicon substrate with a thermally grown oxide dielectric onto which Au source-drain electrodes were deposited. The polymer was then spin-coated on top and annealed to improve the chain packing. The second involved spin-coating the polymer onto a glass substrate followed by the thermal evaporation of top Au source-drain contacts. A polymer insulator was then spin-coated followed by a top Au gate electrode. TOF and SCLC measurements were conducted on diode structures consisting of a polymer layer (of order 1 μm and 100nm respectively) sandwiched between indium-tin-oxide (ITO) or ITO coated with poly (ethylenedioxythiophene)/polystyrene sulphonic acid (PEDOT/PSS) on glass bottom electrode and a Au or Al top electrode. Trapping effects, and the difference between bulk and surface packing can describe the differences of mobilities derived from the three methods. It is interesting to note that they are all within a similar order.

Polyfluorene

Indium tin oxide

Spin Coating

Electron Mobility

Poly(N-isopropylacrylamide)

10.1117/12.506038

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Citations (6)

Organic light-emitting diodes based on lateral-substituted distyrylbenzenes

Materials Science and Engineering C (2002)

John E. Wong Michael S. Weaver T. Richardson Donal D. C. Bradley Duncan W. Bruce

Indium tin oxide

Aluminum Oxide

10.1016/s0928-4931(02)00202-3

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Citations (2)