Proceedings Volume 10101

Organic Photonic Materials and Devices XIX

cover
Proceedings Volume 10101

Organic Photonic Materials and Devices XIX

Purchase the printed version of this volume at proceedings.com or access the digital version at SPIE Digital Library.

Volume Details

Date Published: 10 May 2017
Contents: 12 Sessions, 21 Papers, 25 Presentations
Conference: SPIE OPTO 2017
Volume Number: 10101

Table of Contents

icon_mobile_dropdown

Table of Contents

All links to SPIE Proceedings will open in the SPIE Digital Library. external link icon
View Session icon_mobile_dropdown
  • Front Matter: Volume 10101
  • Nanophotonics I
  • Biophotonics
  • OLEDs
  • Organic Semiconductors
  • Nanophotonics II
  • OPVs
  • Materials I
  • Waveguides/Fiber
  • EO/NLO Polymers
  • Materials II
  • Poster Session
Front Matter: Volume 10101
icon_mobile_dropdown
Front Matter: Volume 10101
This PDF file contains the front matter associated with SPIE Proceedings Volume 10101, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
Nanophotonics I
icon_mobile_dropdown
Nonlinear optical and multiphoton processes for in situ manipulation and conversion of photons: applications to energy and healthcare (Conference Presentation)
Chiral control of nonlinear optical functions holds a great promise for a wide range of applications including optical signal processing, bio-sensing and chiral bio-imaging. In chiral polyfluorene thin films, we demonstrated extremely large chiral nonlinearity. The physics of manipulating excitation dynamics for photon transformation will be discussed, along with nanochemistry control of upconversion in hierarchically built organic chromophore coupled-core-multiple shell nanostructures which enable introduce new, organic-inorganic energy transfer routes for broadband light harvesting and increased upconversion efficiency via multistep cascaded energy transfer. We are pursuing the applications of photon conversion technology in IR harvesting for photovoltaics, high contrast bioimaging, photoacoustic imaging, photodynamic therapy, and optogenetics. An important application is in Brain research and Neurophotonics for functional mapping and modulation of brain activities. Another new direction pursued is magnetic field control of light in in a chiral polymer nanocomposite to achieve large magneto-optic coefficient which can enable sensing of extremely weak magnetic field due to brain waves. Finally, we will consider the thought provoking concept of utilizing photons to quantify, through magneto-optics, and augment - through nanoptogenetics, the cognitive states, thus paving the path way to a quantified human paradigm.
Random optical media based on hybrid organic-inorganic nanowires: multiple scattering, field localization, and light diffusion
L. Persano, M. Moffa, V. Fasano, et al.
Random optical media (ROM) are a novel class of photonic materials characterized by a disordered assembly of the elementary constituents (such as particles, wires and fibers), that determines unique scattering, absorption and emission properties. The propagation of light in ROM is affected by the size and optical properties (refractive index, absorption and emission wavelengths) of their components, as well as by the overall 3-dimensional architecture. So far, most of the investigated ROM have been realized using liquid dispersions or bulk samples embedding colloidal nanoparticles or porous systems. While nanowire-based ROM are poorly investigated, such materials can feature new optical effects related to the elongated shape of their building blocks and to their light-transport properties. Here we report on the fabrication and on the morphological and spectroscopic characterization of hybrid organic-inorganic nanowires, realized by doping polymers with dielectric nanoparticles. We investigate light diffusion and multi-scattering properties of 3- dimensional ROM formed by organic and hybrid nanowires, as well as field localization in 2-dimensional networks. The influence of nanowire geometry and composition on the scattering properties is also discussed.
Biophotonics
icon_mobile_dropdown
Chromophore influence on DNA compactisation (Conference Presentation)
Ileana Rau, Cosmina Andreea Lazar, Antoni C. Mitus, et al.
Our recent research results showed that DNA chains undergo a compactisation when DNA solutions are doped with different chromophores. In this paper we will present our attempt to model this behaviour in order to predict the DNA solutions characterisation.
An optically transparent, flexible, patterned and conductive silk biopolymer film (Conference Presentation)
Transparent, flexible, and conducting films are of great interest for wearable electronics. For better biotic/abiotic interface, the films to integrate the electronics components requires the patterned surface conductors with optical transparency, smoothness, good electrical conductivity, along with the biofriendly traits of films. We focus on silk fibroin, a natural biopolymer extracted from the Bombyx mori cocoons, for this bioelectronics applications. Here we report an optically transparent, flexible, and patterned surface conductor on a silk film by burying a silver nanowires (AgNW) network below the surface of the silk film. The conducting silk film reveals high optical transparency of ~80% and the excellent electronic conductivity of ~15 Ω/sq, along with smooth surface. The integration of light emitting diode (LED) chip on the patterned electrodes confirms that the current can flow through the transparent and patterned electrodes on the silk film, and this result shows an application for integration of functional electronic/opto-electronic devices. Additionally, we fabricate a transparent and flexible radio frequency (RF) antenna and resistor on a silk film and apply these as a food sensor by monitoring the increasing resistance by the flow of gases from the spoiled food.
OLEDs
icon_mobile_dropdown
White light emission from an exciplex interface with a single emitting layer (Conference Presentation)
Wilson Bernal, Enrique Perez-Gutierrez, Andres Agular, et al.
Efficient solid state lighting devices based in inorganic emissive materials are now available in the market meanwhile for organic emissive materials still a lot of research work is in its way. [1,2] In this work a new organic emissive material based on carbazole, N-(4-Ethynylphenyl) carba-zole-d4 (6-d4), is used as electron-acceptor and commercial PEDOT:PSS as the electron-donor to obtain white emission. Besides the HOMO-LUMO levels of materials the white emission showed dependence on the films thicknesses and applied voltages. In here it is reported that by diminishing the thickness of the PEDOT:PSS layer, from 60 to 35 nm, and by keeping the derivative carbazole layer constant at 100 nm the electro-luminescence (EL) changed from emissive exciton states to the mixture of emissive exciton and exciplex states. [3] For the former thicknesses no white light was obtained meanwhile for the later the EL spectra broadened due to the emission of exciplex states. Under this condition, the best-achieved CIE coordinate was (0.31,0.33) with a driving voltage of 8 V. To lower the driving voltage of the devices a thin film of LiF was added between the derivative of carbazol and cathode but the CIE coordinates changed. The best CIE coordinates for this case were (0.29, 0.34) and (0.32, 0.37) with driving voltage of about 6.5 V. Acknowledgments: CeMie-Sol/27 (Mexico) 207450 References [1] Timothy L Dawson, Society of Dyers and Colourists, Color. Technol., 126, 1–10 (2010), doi: 10.1111/j.1478-4408.2010.00220.x [2] G. M. Farinola, R. Ragni, Journal of Solid State Lighting, 2:9 (2015), doi: 10.1186/s40539-015-0028-7. [3] E. Angioni, et al, J. Mater. Chem. C, 2016, 4, 3851, doi: 10.1039/c6tc00750c.
Tuning of the emission color of organic light emitting diodes via smartly designed aluminum plasmonics
Manuel Auer-Berger, Veronika Tretnak, Franz-Peter Wenzl, et al.
With the invention of phosphorescent emitter material, organic light emitting diodes with internal quantum yields of up to 100% can be realized. Still, the extraction of the light from the OLED stack is a bottleneck, which hampers the availability of OLEDs with large external quantum efficiencies. In this contribution, we highlight the advantages of integrating aluminum nanodisc arrays into the OLED stack. By this, not only the out-coupling of light can be enhanced, but also the emission color can be tailored and controlled. By means of extinction- and fluorescence spectroscopy measurements we are able to show how the sharp features observed in the extinction measurements correlate with a very selective fluorescence enhancement of the organic emitter materials used in these studies. At the same time, localized surface plasmon resonances of the individual nanodiscs further modify the emission spectrum, e.g., by filtering the green emission tail. A combination of these factors leads to a modification of the emission color in between CIE1931 (x,y) chromaticity coordinates of (0.149, 0.225) and (0.152, 0.352). After accounting for the sensitivity of the human eye, we are able to demonstrate that this adjustment of the chromaticity coordinates goes is accompanied by an increase in device efficiency.
Enhancing light extraction efficiency in MDMO-PPV based OLEDs by incorporating 250 nm SiO2-colloidal crystals
J. C. Salcedo-Reyes, J. Vázquez, L. C. Jiménez, et al.
In this work, an improvement in light extraction efficiency from MDMO-PPV based OLEDs by using colloidal crystals is demonstrated. The optimal SiO2 sphere diameter for the colloidal crystal was calculated by the Plane Wave Expansion Method (PWEM), taking into account the dispersion relation of the system formed by a face-centered cubic colloidal crystal (FCC) infiltrated within the luminescent polymer MDMO-PPV. The fabrication method of such a polymer layer with a photonic crystal beneath by spin coating was proved and patented. Therefore, devices with the structure ITO/PEDOT/MDMO-PPV+SiO2 colloidal crystal/Ag were elaborated. Compared with standard OLEDs containing a single MDMO-PPV luminescent layer, the external quantum efficiency of devices modified with a colloidal crystal matrix within the MDMO-PPV layer shows a significant increment, as evaluated from the optical power as a function of applied bias for both kinds of devices.
Light coupling in polymer nanofibers: from single-photon emission to random lasing
A. Camposeo, M. Gaio, M. Moffa, et al.
The understanding of the phenomena underlying the interaction of photons with dielectric, metallic and hybrid microand nano-structures and the development of advanced fabrication tools have paved the way to the realization of complex, nanostructured photonic structures, with tailored and exotic absorption and emission properties. Among such nanostructured materials, polymer nanofibers have intriguing and specific properties: they can embed molecular and quantum dot light sources, they can transport light among distant emitters and they can be arranged in 2-dimensional and 3-dimensional architectures in a controlled fashion, forming complex networks of interacting light emitters. However, coupling of light with polymer nanofibers depends on many variables, being often limited by the arrangement and positioning of the nanoscale light-sources, and by the fiber geometry. Here we report on the fabrication of active polymer nanofibers with improved surface properties and controlled geometry by electrospinning. Polarization and momentum spectroscopy of light emitted by molecular compounds and single quantum dots embedded in electrospun polymer fibers, evidence that efficient, nanostructured photon sources with targeted polarization and coupling efficiency can be realized in nanofiber-based photonic environments.
Organic Semiconductors
icon_mobile_dropdown
Time-resolved measurement of intramolecular photoinduced electron transfer processes in perylene diimides (Conference Presentation)
Robin Carl Döring, Eduard Baal, Jörg Sundermeyer, et al.
Perylene-3,4,9,10-tetracarboxylic acid (PTCDA) and respective derivatives (e.g. perylene diimide - PDI) are widely used as dyes but also for device applications such as organic field effect transistors or in organic photovoltaics. Due to their intrinsically high quantum efficiencies they are also used as spectroscopic standards. One major drawback of these materials is their low solubility in organic solvents which can be addressed by long alkyl substitutions. When introducing a tertiary amine into the molecule a mechanism known as photoinduced electron transfer (PET) can occur. Here, following an optically excited HOMO-LUMO transition of the core, an electron from the electron lone pair of the amine is transferred to the HOMO of the perylene core. Hence, radiative recombination is disallowed and photoluminescence effectively quenched. Here, we perform a systematic study of the distance dependence of the PET by introducing alkyle groups as spacer units between PDI core and the tertiary amine. Dynamics of the PET are extracted from ultrafast time-resolved photoluminescence measurement data. A rate equation model, simulating a three level system, reveals rate constant of the back electron transfer, otherwise not accessible with our experimental methods. Assuming a Marcus model of electron transfer, electronic coupling strength between the electronic states involved in the respective transitions can be calculated. In addition to the distance dependence, the effects of protonation and methylation of the the tertiary amine units are studied.
Carrier dynamics in pentacene-perfluropentacene heterocrystals (Conference Presentation)
Andre Rinn, Tobias Breuer, Greogor Witte, et al.
Aromatic molecules are among the most promising materials in the field of organic optoelectronic due to the favorable properties of the delocalized -electron system present in those molecules. One of the most studied systems in this material class is the planar molecule of pentacene. An interesting application for pentacene is the incorporation into a donor-acceptor heterojunction in combination with its perfluorinated counterpart. Such samples may be deposited as intermixed blends (molecular alloys) or as alternating layered stacks. The out-of-plane delocalized -electron systems cause significant intermolecular coupling, even enabling the formation of charge-transfer excitons across heterointerfaces. Hence, studying this model system forms the optimal platform to investigate excitation transfer and charge separation in organic solar cells. We present a comprehensive study of the optical properties of pentacene -perfluoropentacene heterosystems. The samples are grown as crystalline thin films in different molecular configurations: either layered or as intermixed blends, both, in standing and lying molecular orientation. Time resolved luminescence and linear absorption spectroscopy are performed to obtain the carrier dynamics of the charge transfer states and response of the pure materials. The influence of different packing motifs on the optical properties is investigated, revealing a radiationless long-range energy transfer in addition to the local occupation of charge-transfer states.
Nanophotonics II
icon_mobile_dropdown
Surface-confined supramolecular self-assembly: towards nano-optics on graphene (Conference Presentation)
André-Jean Attias, Ping Du, David Kreher, et al.
In view of the demanding forthcoming applications in nanooptics, it is of prime interest to create functions out-off the plane and to fully exploit the room above the substrate. Accessing the dimension perpendicular to the substrate is so a mandatory step to achieve the decoupling from conducting substrate. Here we present a series of 3D organic building blocks able to self-assemble on flat sp2-carbon based substrates like graphene and expose a chromophore decouled from the surface. The chromophores range from fluorescent dyes to photoswitchable molecules. We will present the optical properties in solution as well as the properties of the self-assembled functional monolayers on flat sp2-carbon based substrates. The first fluorescent molecular self-assembly on graphene will be reported
Single molecule-level study of donor-acceptor interactions and nanoscale environment in blends
Nicole Quist, Rebecca Grollman, Jeremy Rath, et al.
Organic semiconductors have attracted considerable attention due to their applications in low-cost (opto)electronic devices. The most successful organic materials for applications that rely on charge carrier generation, such as solar cells, utilize blends of several types of molecules. In blends, the local environment strongly influences exciton and charge carrier dynamics. However, relationship between nanoscale features and photophysics is difficult to establish due to the lack of necessary spatial resolution. We use functionalized fluorinated pentacene (Pn) molecule as single molecule probes of intermolecular interactions and of the nanoscale environment in blends containing donor and acceptor molecules. Single Pn donor (D) molecules were imaged in PMMA in the presence of acceptor (A) molecules using wide-field fluorescence microscopy. Two sample configurations were realized: (i) a fixed concentration of Pn donor molecules, with increasing concentration of acceptor molecules (functionalized indenflouorene or PCBM) and (ii) a fixed concentration of acceptor molecules with an increased concentration of the Pn donor. The D-A energy transfer and changes in the donor emission due to those in the acceptor- modified polymer morphology were quantified. The increase in the acceptor concentration was accompanied by enhanced photobleaching and blinking of the Pn donor molecules. To better understand the underlying physics of these processes, we modeled photoexcited electron dynamics using Monte Carlo simulations. The simulated blinking dynamics were then compared to our experimental data, and the changes in the transition rates were related to the changes in the nanoscale environment. Our study provides insight into evolution of nanoscale environment during the formation of bulk heterojunctions.
Graphene and silver-nanoprism dispersion for printing optically-transparent electrodes
Optically transparent electrodes (OTEs) are used for bioelectronics, touch screens, visual displays, and photovoltaic cells. Although the conductive coating for these electrodes is often composed of indium tin oxide (ITO), indium is a very expensive material and thin ITO films are relatively brittle compared to conductive polymer or graphene thin films. An alternative highly conductive optically transparent thin film based on a graphene (G) and silver-nanoprism (AgNP) dispersion is introduced in this paper. The aqueous G ink is first synthesized using carboxymethyl cellulose (CMC) as a stabilizing agent. Silver (Ag) nanoprisms are then prepared separately by a simple thermal process which involves the reduction of silver nitrate by sodium borohydride. These Ag nanoprisms are only a few nanometers thick but have relatively large surface areas (>1000 nm2). As a consequence, the nanoprisms provide more efficient injection of free carriers to the G layer. The concentrated G-AgNP dispersions are then deposited on optically transparent glass and polyimide substrates using an inkjet printer with a HP6602A print head. After printing, these optically thin films can be thermally treated to further increase electrical conductivity. Thermal treatment decomposes CMC which frees elemental carbon from polymer chain and, simultaneously, causes the film to become hydrophobic. Preliminary experiments demonstrate that the G-AgNP films on glass substrates exhibit high conductivity at 70% transparency (550 nm). Additional tests on the Gr-AgNP thin films printed on polymide substrates show mechanical stability under bending with minimal reduction in electrical conductivity or optical transparency.
OPVs
icon_mobile_dropdown
Planar heterojunction perovskite solar cells fabricated by wet process
Tetsuya Taima, Kohei Yamamoto, Md. Shahiduzzaman, et al.
Organic-inorganic hybrid perovskite materials have been recently emerged as a promising cost- and energy efficient light absorber material for photovoltaic applications. Unfortunately, perovskite solar cells have a problem with decreacement of power conversion efficiency due to degradation in the air. To detect the reason of degradation on perovskite solar cells, we exposed deposited CH3NH3PbI3 and HC(NH2)2PbI3 films to the O2 or (H2O+N2) atmosphere condition. Analysis of the film revealed that the large energy band gap was shown due to influence of H2O molecule in CH3NH3PbI3 and HC(NH2)2PbI3. In (H2O+N2) atmosphere conditions, the existence of CH3NH3I and HC(NH2)2I molecule has found to affect the morphology, absorption and as well as crystalline diffraction peak. The resultant perovskite crystalline structure was degraded by H2O molecules in the air exposure condition.
Organometallic perovskite solar cells: a study of temperature effect (Conference Presentation)
It is highly desirable to develop new solar cells to operate at temperatures higher and lower than standard operational conditions for space and near space applications in future. Herein, we communicate an experimental investigation on temperature-dependent photovoltaic efficiency for perovskite solar cells based on mesoscopic TiO2/Al2O3/NiO/carbon architecture. This perovskite device shows impressive 5% power conversion efficiency at low temperature of 80 K. Therefore, the perovskite solar cells can be precisely characterized in a wide temperature range, which enables unequivocal identification of the contribution of CH3NH3PbI3 perovskite to construction of the built-in electric field, and thus, the temperature dependent photovoltaic parameters. The latter, particularly the open-circuit voltage, shows a strong dependence on the dielectric constant of CH3NH3PbI3.
Charge carrier dynamics at the pentacene-C60 interface (Conference Presentation)
Robin Carl Döring, Andrea Karthäuser, Tobias Breuer, et al.
Organic molecular solids feature various properties considered advantageous for next-generation photovoltaic devices such as mechanical flexibility and ease of fabrication by, e.g., large-scale and large volume printing. Additionally, Singlet-Exciton Fission may allow surpassing the Shockley-Queisser limit. Here, one photoexcited singlet-type exciton decays into two triplet-type excitons, effectively doubling the number of excited charge carriers. Hence, above-unity quantum efficiencies may be achieved in photovoltaics and have been reported in for example, pentacene (PEN) –C60 heterojunctions. Here, we study the carrier dynamics at well-defined PEN-C60 interface model systems by time-resolved photoluminescence spectroscopy experiments for different excitation photon energies. Thereby, we disentangle charge transfer and excitation dynamics, i.e., injection, transport, dissociation, and extraction. The photoluminescence spectra reveal two distinct transition energies associated with charge-transfer (CT) states expected from photoelectron spectroscopy experiments. These long-lived transitions show a clear dependence on excitation energy, corroborating the proposed CT transitions and revealing the fact that carriers need to be created in both individual constituents for CT transitions to be observable. Additionally, the C60 photoluminescence efficiency strongly quenches for increasing PEN coverage while the lifetime is drastically enhanced yielding strong evidence for an electron transfer between the PEN ground state and C60 when only the latter is photoexcited.
Spectroscopic investigation of squaraine dyes
Giuseppe Maria Paternò, Simone Galliano, Nadia Barbero, et al.
We report a study on the excited state dynamics of two symmetric squaraine dyes, carrying different side-groups attached to the squaric ring. By means of UV-VIS absorption and time-resolved fluorescence spectroscopies, we found that the photodynamic of these functional molecules depends strongly on both the steric and electro-donating properties of the side-group.
Materials I
icon_mobile_dropdown
Photothermal effect in conductive polymer layers for structural conversion into a complex 3D structure (Conference Presentation)
Eunkyoung Kim, HanWhuy Lim, Jongbeom Na
The conversion of photons to heat in the conductive polymer films causes local heating to increase temperature at the light exposed area. The resultant heat can be converted into other type of energy such as electrical, mechanical, or chemical energy. In particular, photothermal effect in conductive polymer layers could be used for structural changes of the 2D structures into a complex three-dimensional (3D) structure. Herein we report the preparation of photothermal conductive polymer layers (CPL) and the integration of CPLs into a 2D structured film, to optimize not only the light-to-heat but also 2D-to-3D structural conversion.
Photoanisotropy in polarization-sensitive polymer materials based on the media with covalently-bonded components
The well-known scalar photochromism phenomenon is a reversible phototransformation of chemical species between two forms having different absorption spectra. It is observed under the action of actinic light regardless of its polarization state. Unlike this in some high-efficient polarization-sensitive azopolymeric materials, we have observed a welldeveloped vector polyphotochromism which appears as a light-induced area with spectral selectivity for the linearly polarized probing beams. A sharp change in the transmission spectrum of the material have been observed when we placed an irradiated area of the sample between crossed polarizers, while the transmission spectrum of the sample remained practically unchanged in case of probing by unpolarized light. The effect has a purely vector nature, while the transmission spectrum of the exposed material essentially changes in case of observing between crossed polarizers and the change in the spectrum unambiguously depends on the energy exposure. A significant dependence of the kinetic of the vector polyphotochromism induction on the power density of linearly polarized actinic light (445 nm) is shown for probing beam of 635 nm. It is also shown that the kinetics of the effect depends on the photosensitive layer thickness and the concentration of the chromophore. The experiments were carried out for two synthesized side-chain azopolymers obtained as immobilized polar azo dyes on polymethylmethacrylate backbone. It is clearly shown a light-controlled spectral selectivity of the sample activated by the various doses of the stimulating radiation.
Fungi-derived pigments as sustainable organic (opto)electronic materials
Robert Harrison, Alexander Quinn, Genevieve Weber, et al.
We present photophysical and optoelectronic properties of xylindein and optical properties of two other fungi-derived organic pigments. Photophysics of these materials is determined by the interplay of inter- and intramolecular hydrogen bonding, which was systematically explored using absorption and photoluminescence spectroscopy of xylindein in various solutions, pH buffers, and in the solid state. Amorphous xylindein films yielded a lower bound on the charge carrier mobility of 0.2-0.5 cm2=(V•s) and exhibited photocurrent upon photoexcitation in the ultraviolet and visible wavelength range. Thermal and photostability of xylindein was also characterized, and it considerably exceeded that of conventional organic semiconductors such as pentacene derivatives.
Waveguides/Fiber
icon_mobile_dropdown
Photoinduced (anomalous) dynamics of functionalized polymer chains: Applications for Surface Relief Grating modelling
T. Wysoczanski, A. C. Mitus, W. Radosz, et al.
Recently we have formulated a generic Monte Carlo model for the photoinduced build up of the density grating and surface relief grating (SRG) in a model polymer matrix functionalized with azo–dyes.1 Mass transport from illuminated to dark places was demonstrated and ascribed to a hypothetical complex dynamics of polymer chains in bond–fluctuation model. This paper constitutes a first step towards verification of this hypothesis: we characterize the motion of single functionalized chain dependent on the intensity of linearly polarized light illumination. We report various regimes of diffusion of the center of mass (CM) of the chain: subdiffusion, normal diffusion and superdiffusion. Presence/absence of those regimes depends on the light intensity and on the length of the chain. We report a surprising effect in the presence of light illumination: the longer the polymer chain the stronger superdiffusion sets in.
Flexible thin polymer waveguide Bragg grating sensor foils for strain sensing
This paper demonstrates that epoxy-based single mode polymer waveguides with Bragg gratings can be realized in very thin (down to 50 micron) polymer foils which are suitable for strain sensing when integrated inside glass fiber reinforced polymer composite materials. The single mode waveguides were fabricated using laser direct-write lithography and the gratings were realized using nanoimprint lithography. These steps were performed on a temporary rigid carrier substrate and afterwards the functional layers were released yielding the thin, flexible sensor foils which can be laser-cut to the required dimensions. The Bragg grating-based polymer waveguide sensor foils were characterized before and after embedding into the composite. As expected, there was a blue shift in the reflection spectrum because of residual strain due to the embedding process. However, the quality of the signal did not degrade after embedding, both for 50 and 100 micron thick sensor foils. Finally, the sensitivity to strain of the embedded sensors was determined using a tensile test and found to be about 1 pm / microstrain.
Multi-layered fabrication of large area PDMS flexible optical light guide sheets
Large area polydimethylsiloxane (PDMS) flexible optical light guide sheets can be used to create a variety of passive light harvesting and illumination systems for wearable technology, advanced indoor lighting, non-planar solar light collectors, customized signature lighting, and enhanced safety illumination for motorized vehicles. These thin optically transparent micro-patterned polymer sheets can be draped over a flat or arbitrarily curved surface. The light guiding behavior of the optical light guides depends on the geometry and spatial distribution of micro-optical structures, thickness and shape of the flexible sheet, refractive indices of the constituent layers, and the wavelength of the incident light. A scalable fabrication method that combines soft-lithography, closed thin cavity molding, partial curing, and centrifugal casting is described in this paper for building thin large area multi-layered PDMS optical light guide sheets. The proposed fabrication methodology enables the of internal micro-optical structures (MOSs) in the monolithic PDMS light guide by building the optical system layer-by-layer. Each PDMS layer in the optical light guide can have the similar, or a slightly different, indices of refraction that permit total internal reflection within the optical sheet. The individual molded layers may also be defect free or micro-patterned with microlens or reflecting micro-features. In addition, the bond between adjacent layers is ensured because each layer is only partially cured before the next functional layer is added. To illustrate the scalable build-by-layers fabrication method a three-layer mechanically flexible illuminator with an embedded LED strip is constructed and demonstrated.
Polymer optical fibers doped with organic materials as luminescent solar concentrators
This paper provides an analysis of the emission properties of different polymer optical fibers doped with organic materials with the aim of investigate their performance as luminescent solar concentrators. We present a study of the light propagation along the fibers, together with the experimental measurements of two different efficiencies: side illumination coupling efficiency and fluorescent fiber solar concentrator efficiency. The results obtained for all the fibers are compared and discussed.
EO/NLO Polymers
icon_mobile_dropdown
Effect of charge carrier blocking, surface resistance and electric field distribution on electric field poling of nonlinear optic polymers
In our previous work we introduced charge carrier blocking layers to realize an increase in the poling field and, hence, an increase in the nonlinearity, or electro-optic (EO) coefficient, r33, of the nonlinear optic (NLO) polymer disperse red 1:polymethylmethacrylate (DR1:PMMA). In addition, we not only achieved higher poling voltages, which resulted in higher r33s at these higher poling voltages, but we also observed higher r33s when both the samples with and without the charge carrier blocking layers were poled at the same poling voltage. We attributed that primarily to a decrease in the surface resistance. Here we provide a more detailed analysis and propose that the increase may be attributed not only to surface resistance but a combination of lower surface resistance, more uniform electric field distribution and charge carrier blocking, provided by the charge carrier blocking layers.
Nonlinear optics in organic cavity polaritons (Conference Presentation)
Coupling between excitons belonging to organic dyes and photons in a microcavities forming cavity polaritons have been receiving attention for their fundamental interest as well as potential applications in coherent light sources. Organic materials are of particular interest as the coupling is particularly strong due to the large oscillator strength of conjugated organic molecules. The resulting coupling in organic materials is routinely in the strong regime. Ultrastrong coupling between photons and excitons in microcavities containing organic dyes and semiconductors has been recently observed in room temperature. We have studied the coupling between cavity pairs in the ultrastrong regime and found that the high order terms in the modified Jaynes-Cummings model result in broken degeneracy between the symmetric and antisymmetric modes. The unusually strong coupling between cavity photons and organic excitons dovetail with the robust nonlinear optical responses of the same materials. This provides a new and promising hybrid material for photonics. We report on measurements of photorefraction in organic cavities containing a derivative of the photorefractive organic glass based on 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (DCDHF).
Materials II
icon_mobile_dropdown
Graphene-based organic-inorganic hybrids with optoelectronic and magneto-optic functions (Conference Presentation)
Kwang-Sup Lee, Sung-Hyun Kim, Juhyoung Jung, et al.
Groups around the world are pursuing optoelctronic and magneto-optic properties of graphene-based materials since they hold a lot of promise for future technologies. Quantum dot (QD) decorated graphenic nanohybrids can be candidates for demonstrating energy transfer, while magnetic nanoparticles (MNPs) on graphene give rise to interesting electronic phenomena like magneto-optical effects. Graphene containing MNPs are also good candidates for exploring quantum-hall effect. In medicine these materials have demonstrated applications in bioimaging, drug delivery, photothermal treatment and magnetic resonance imaging. A majority of groups working on QD or MNPs have focused on chemical functionalization methods for making graphene-MNP nanohybrids. We have developed a set of small molecule as well as polymeric ligands for noncovalent self-assembly of nanoparticles on graphene. The ligands contain pyrene as an anchor group for graphene and also thiol or dipamine as anchor groups for QD or MNPs. In this presentation we discuss the synthesis and characterization of these materials and outline some early results regarding exploratory device fabrication involving these materials.
Additive manufacturing of tunable lenses
Katja Schlichting, Tobias Novak, Andreas Heinrich
Individual additive manufacturing of optical systems based on 3D Printing offers varied possibilities in design and usage. In addition to the additive manufacturing procedure, the usage of tunable lenses allows further advantages for intelligent optical systems. Our goal is to bring the advantages of additive manufacturing together with the huge potential of tunable lenses. We produced tunable lenses as a bundle without any further processing steps, like polishing. The lenses were designed and directly printed with a 3D Printer as a package. The design contains the membrane as an optical part as well as the mechanical parts of the lens, like the attachments for the sleeves which contain the oil. The dynamic optical lenses were filled with an oil. The focal length of the lenses changes due to a change of the radius of curvature. This change is caused by changing the pressure in the inside of the lens. In addition to that, we designed lenses with special structures to obtain different areas with an individual optical power. We want to discuss the huge potential of this technology for several applications. Further, an appropriate controlling system is needed. We´ll show the possibilities to control and regulate the optical power of the lenses. The lenses could be used for illumination tasks, and in the future, for individual measurement tasks. The main advantage is the individuality and the possibility to create an individual design which completely fulfills the requirements for any specific application.
Change of electric dipole moment in charge transfer transitions of ferrocene oligomers studied by ultrafast two-photon absorption
Alexander Mikhaylov, Eduardo Arias, Ivana Moggio, et al.
Change of permanent electric dipole moment in the lower-energy charge transfer transitions for a series of symmetrical and non-symmetrical ferrocene-phenyleneethynylene oligomers were studied by measuring the corresponding femtosecond two-photon absorption cross section spectra, and were determined to be in the range Δμ = 3 – 10 D. Quantum-chemical calculations of Δμ for the non-symmetrical oligomers show good quantitative agreement with the experimental results, thus validating two-photon absorption spectroscopy as a viable experimental approach to study electrostatic properties of organometallics and other charge transfer systems.
Additive manufacturing: a new approach to realize complex and unconventional optical components
Andreas Heinrich, Manuel Rank, Sangeetha Suresh Nair, et al.
In recent years, additive manufacturing methods became more and more prominent. Thereby, these techniques are mainly used in order to realize mechanical components. But the additive manufacturing technology offers a high potential in the field of optics as well. Owing to new design possibilities, completely new solutions are possible. We report on the realization of complex freeform optics using standard 3D printers. We briefly point out the characteristics of 3D printing and its influence on the optical properties. Additionally we address the needed rework of 3D printed optical components. Therefore we apply two different methods - a robot-based fluid jet polishing and a coating method. The advantage of a 3D printed optic lies in its shape complexity. Thus different complex shaped optical elements are discussed. They are used for either metrology tasks or illumination tasks.
Poster Session
icon_mobile_dropdown
Deep-blue light emission with a wide-bandgap naphthalene-derivative liquid organic semiconductor host
Naofumi Kobayashi, Hiroyuki Kuwae, Juro Oshima, et al.
We developed a novel naphthalene-derivative to function as a wide-bandgap liquid organic semiconductor (LOS) host material for the limited range of liquid deep-blue light-emitting materials that have been developed to date. The naphthalene-derivative, 1-naphthaleneacetic acid 2-ethylhexyl ester (NLQ) was synthesized as a LOS, by introducing an ethylhexyl group into naphthalene. 9,10-Diphenyl anthracene (DPA) was doped into NLQ as a guest deep-blue dye. From the absorption spectrum, the bandgap energy of NLQ was estimated to be 4.13 eV, indicating that NLQ has the widest bandgap energy of any such host material so far as we know. Deep-blue electroluminescence (EL) emission in a liquid state was obtained by doping DPA into NLQ. Light emission could be achieved by a combination of Förster resonance energy transfer and direct recombination of trapped holes and electrons because the bandgap energy of DPA is straddle by that of the wide-bandgap NLQ. Thus, NLQ is shown to be a promising wide-bandgap LOS host material, which allows deep-blue light emission and may have applications in liquid organic light-emitting diodes.
Influences of device structures on microstructure-correlated photovoltaic characteristics of organic solar cells
Fu-Chiao Wu, Cheng-Chi Yang, Po-Tsung Tseng, et al.
Photovoltaic characteristics of organic solar cells (OSCs) are correlated with microstructural qualities of active layers (ALs). Numerous efforts focused on improving process conditions of ALs to attain effective microstructures to achieve high-efficiency OSCs. Aside from AL process conditions, layer properties under AL can also influence microstructural qualities of AL. In this study, we adopted poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61-butyric acid methyl ester (PCBM) mixture as AL, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as hole extraction layer, and branched polyethyleneimine (BPEI) as electron extraction layer to prepare OSCs with different device structures, that is, normal type (PEDOT:PSS/P3HT:PCBM/BPEI) and inverted type (BPEI/P3HT:PCBM/PEDOT:PSS) structures. We discovered that although devices have similar layer components, they have different photovoltaic characteristics. Inverted devices demonstrated higher power conversion efficiency than normal devices. Various methods, including absorption spectroscopy and microscopy, were used to study AL microstructures of different devices. We observed that P3HT crystallites grown on BPEI had longer vertical size and shorter horizontal size compared with those grown on PEDOT:PSS; these properties could result from larger interfacial tension of P3HT with BPEI than with PEDOT:PSS. Observed shape of P3HT crystallites in inverted devices facilitated efficient charge transport to electrodes and suppressed current leakage. As a result, inverted devices generated improved photovoltaic performance.