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Recent News

Our paper "Plasmonic Sphere-on-Plane Systems with Semiconducting Polymer Spacers Layers" by Binxing Yu, et al., was accepted for publication in the journal Physical Chemistry Chemical Physics.

Our paper "Aperiodic Porous Metasurface Mediated Organic Semiconductor Fluorescence" by Zeqing Shen, et al., was accepted for publication in ACS Photonics.

Congratualations to Catrice Carter and Zeqing Shen on your successful PhD defenses!! Best of luck in your future careers at Intel and Duke University.

Ankur Dalsania was awarded a prestigious Henry Rutgers Scholar Award from SAS for his honors senior thesis "Enhancing Organic Polymer Exciton-Plasmon Coupling for Applications in Optoelectronics." Congratulations and best wishes for med. school!

Prof. O'Carroll gave an invited talk on the "Influence of Conjugated Polymer Thin-
Film Morphology and Exciton-
Plasmon Coupling on Nanophotonic
Light Trapping and Light Extraction
" at the ACS PMSE Young Investigator Symposium during the Spring ACS National Meeting in San Francisco.

Congratulations to Anand Patel on his undergraduate poster award for his work on nanoimprint lithography of silver ink at the 2017 MGM Symposium!

12/16/2016: Congratulations to Chris Petoukhoff on his successful PhD defense!! Best of luck with your postdoc. position in OIST!

The paper "Ultrafast Charge Transfer and Enhanced Absorption in MoS2 - Organic van der Waals Heterojunctions using Plasmonic Metasurfaces," by C. E. Petoukhoff et al. arising from Chris's NSF-EAPSI research in the Dani Group in Japan has been accepted for publication in ACS Nano.

The paper "Achieving Highly Efficient and Robust Hybrid Semiconductor Lighting Phosphors via Incorporation of Strongly Emissive Cu4I4 Cubic Core into Extended Network Structures," by Y. Fang et al. from the group of our collaborator Jing Li was accepted for publication in Advanced Functional Materials.

Congratulations to Zeqing on being selected as a finalist for the prestigious Graduate Student Award at the 2016 Materials Research Society Fall Meeting!

The paper "Effects of Metal Film Thickness and Gain on the Coupling of Organic Semiconductor Exciton Emission to Surface Plasmon Polaritons" by Dalsania et al. was accepted for publication in the Journal of Materials Chemsitry C.

Our paper "Cost, Energy and Emissions Assessment of Organic Polymer Light-Emitting Device Architectures" by Carter et al. was accepted for publication in The Journal of Cleaner Production.

Dr. O'Carroll gave an invited talk on organic exciton-plasmonic metasurface interactions at the META 2016 conference in Torremolinos, Spain.

Our paper "Effects of Conjugated Polymer Incorporation on the Morphology and Energy Harvesting of Solution-Processed Phthalocyanine-Based Thin-Films" by Cheung et al. was accepted for publication in the journal Synthetic Metals.

Thank you to our RiSE summer undergraduate researcher Kelsey Gwynne and our TARGET VI high-school students for their excellent work this summer! Also, thanks to Catrice and the rest of the group for all of their mentorship and help this summer!

Dr. O'Carroll was selected as a 2017 ACS Polymer Materials Science and Engineering (PMSE) Young Investigator.

Ankur received numerous awards at the CCB Undergraduate Symposium: Phyllis Dunbar Award for Excellence in Physical Chemistry; Ning-Moeller Award; CCB Undergraduate Service Award; Chemical Resources Award.

Ankur was awarded a fellowship from the NASA NJ Space Grant Consortium for development of low-threshold, thin-film organic lasers.

Cate won an award for her senior thesis research poster on inverted polymer OLEDs at the 2016 MGM Symposium.

Dr. O'Carroll gave an invited seminar at Trinity College Dublin.

Congratulations to Binxing on his successful PhD thesis defense!

Congratualtions to Jill on passing her in-field research proposal!

Dr. O'Carroll gives an invited talk on exciton-metasurface interactions at the APS March meeting.

More news here...
  O'Carroll Research Group
Nanophotonics and Organic Optoelectronics
The O'Carroll Group studies light generating and light harvesting processes in organic polymer semiconductor materials and plasmonic nanostructures. Our research has a number of uses such as: light-management in thin-film organic opto-electronic devices; optically-active electrodes; nanoscale optical devices; and environmentally-friendly electronics and photonics.

Research Highlights:
Ultrafast Charge Transfer and Enhanced Absorption in MoS2–Organic van der Waals Heterojunctions Using Plasmonic Metasurfaces
C. E. Petoukhoff, B. M. K. Mariserla, D. Voiry, I. Bozkurt, S. Deckoff-Jones, M. Chhowalla, D. M. O'Carroll, K. Dani, ACS Nano 10, 9899-9908 (2016).

Hybrid organic–inorganic heterostructures are attracting tremendous attention for optoelectronic applications due to their low-cost processing and high performance in devices. In particular, van der Waals p–n heterojunctions formed between inorganic two-dimensional (2D) materials and organic semiconductors are of interest due to the quantum confinement effects of 2D materials and the synthetic control of the physical properties of organic semiconductors, enabling a high degree of tunable optoelectronic properties for the heterostructure. However, for photovoltaic applications, hybrid 2D–organic heterojunctions have demonstrated low power conversion efficiencies due to the limited absorption from constraints on the physical thickness of each layer. Here, we investigate the ultrafast charge transfer dynamics between an organic polymer:fullerene blend and 2D n-type MoS2 using transient pump–probe reflectometry. We employ plasmonic metasurfaces to enhance the absorption and charge photogeneration within the physically thin hybrid MoS2–organic heterojunction. For the hybrid MoS2–organic heterojunction in the presence of the plasmonic metasurface, the charge generation within the polymer is enhanced 6-fold, and the total active layer absorption bandwidth is increased by 90 nm relative to the polymer:fullerene blend alone. We demonstrate that MoS2–organic heterojunctions can serve as hybrid solar cells, and their efficiencies can be improved using plasmonic metasurfaces.
  image file: c6tc02552h-f1.tif
Effects of metal film thickness and gain on the coupling of organic semiconductor exciton emission to surface plasmon polaritons
A. K. Dalsania, J. Kohl, C. E. Kumah, Z. Shen, C. E. Petoukhoff, C. M. Carter, D. M. O’Carroll, J. Mater. Chem. 4, 10111-10119 (2016)

Control of near-field exciton emission coupling to surface plasmon polaritons (SPPs) is of importance for the development of efficient organic semiconductor thin-film light sources. Here, we experimentally investigate organic exciton emitter–SPP coupling in insulator–semiconductor–metal–insulator (ISMI) waveguides, containing an organic semiconducting (i.e., conjugated) polymer film on a range of Ag metal film thicknesses, as a function of optical excitation pump power and collection polarization. An increase in transverse-magnetic-polarized emission peak intensity is observed as a function of decreasing metal film thickness from ISMI waveguides at high excitation powers, suggesting more efficient emitter–SPP coupling for thinner Ag films when the polymer undergoes stimulated emission. Furthermore, emission dichroic ratio values (defined as the ratio of transverse electric to transverse magnetic polarized emission) increase when the polymer undergoes stimulated emission for thicker metal films but decrease below a certain metal film thickness. This indicates that gain in the semiconducting polymer film reduces the extent of exciton emission coupling to SPP modes for thicker metal films. However, once the metal thickness is below a critical value, gain improves exciton–SPP coupling. These results are consistent with theoretical calculations, which show that the dominant SPP mode exhibits a greater propagation length for thinner metal films, suggesting greater near-field overlap between the semiconductor film and SPP modes.
Cost, energy and emissions assessment of organic polymer light-emitting device architectures
C. M. Carter, J. Cho, A. Glanzer, N. Kamcev, D. M. O'Carroll, J. Cleaner Prod. 137, 1418-1431 (2016).

Abstract: Proponents for sustainable alternative lighting and display options advocate for organic light-emitting diodes (OLEDs), particularly polymer-based organic light-emitting diodes (P-OLEDs), because of their potential for low-cost fabrication, more versatile device formats and lower power consumption compared to traditional options. Here, an economic, energy and CO2 emissions assessment is carried out for four different laboratory-scale, blue-emitting P-OLED device architectures: bottom-emitting conventional; bottom-emitting inverted; top-emitting conventional; and top-emitting inverted. Additionally, comparisons with a standard, commercial-scale, blue inorganic light-emitting diode (LED) device architecture are made. The various P-OLED device architectures are investigated due to their potential to increase operational lifetime (inverted) and light out-coupling efficiency (top-emitting). The following metrics are used in this assessment: device cost per area; yearly operating cost; optical power cost; CO2 emissions from device production; and yearly operating CO2 emissions. We show that the top-emitting inverted device architecture significantly reduces the device cost per area, yearly operating cost, optical power cost and CO2 emissions for the P-OLED devices, due to elimination of indium tin oxide and its comparatively high luminous efficacy and longer lifetime. In addition, the top-emitting inverted P-OLED device architecture performs competitively at the laboratory scale with commercial-scale inorganic LEDs for all metrics. However, if top-emitting P-OLEDs are to be manufactured on a large scale, the luminous efficacy assumed for laboratory-scale devices needs to remain constant throughout development to remain competitive.
Absorption-Induced Scattering and Surface Plasmon Out-Coupling from Absorber-Coated Plasmonic Metasurfaces
C. E. Petoukhoff, D. M. O'Carroll, Nat. Commun. 6, 7899-1-13 (2015).

Abstract: Interactions between absorbers and plasmonic metasurfaces can give rise to unique optical properties not present for either of the individual materials and can influence the performance of a host of optical sensing and thin-film optoelectronic applications. Here we identify three distinct mode types of absorber-coated plasmonic metasurfaces: localized and propagating surface plasmons and a previously unidentified optical mode type called absorption-induced scattering. The extinction of the latter mode type can be tuned by controlling the morphology of the absorber coating and the spectral overlap of the absorber with the plasmonic modes. Furthermore, we show that surface plasmons are backscattered when the crystallinity of the absorber is low but are absorbed for more crystalline absorber coatings. This work furthers our understanding of light–matter interactions between absorbers and surface plasmons to enable practical optoelectronic applications of metasurfaces.
Mode-specific study of nanoparticle-mediated optical interactions in an absorber/metal thin film system
B. Yu, J. Woo, M. Kong, D. M. O'Carroll, Nanoscale 7, 13196-13206 (2015).

Abstract: We present an experimental and theoretical study of the electromagnetic interaction between a single gold nanoparticle and a thin gold substrate separated by a sub-50 nm-thick optically absorptive polythiophene spacer layer. Single-particle dark-field scattering spectra show distinct resonance features assigned to four different modes: a horizontal image dipole coupling mode, a vertical image dipole coupling mode and horizontal and vertical coupling modes between localized surface plasmon resonances (LSPRs) and surface plasmon polaritons (SPPs). Relatively broadband spectral tuning of the modes can be achieved by modification of the thickness of either the absorptive spacer or the underlying metal film. Dark-field images also reveal the existence of particles for which the signal of the horizontal image dipole coupling mode is suppressed. This is attributed to partial-embedding of gold nanoparticles into the polythiophene spacer and leads to higher scattered light intensities at longer wavelengths. Furthermore, we find absorption enhancement in the semiconducting polythiophene spacer increases with decreasing spacer thickness, indicating the increased light trapping ability of the gold nanoparticles for ultra-thin semiconductor layers. The need for ever-thinner semiconductor layers in optoelectronic devices requires effective light trapping at deeply-subwavelength scales. This work demonstrates that light trapping in sub-50 nm-thick semiconductor layers is possible using a “sphere-on-plane” system and offers insight into how coupling modes can be manipulated in this system.