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Recent News

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.

Catrice gives a talk on her OLED research at the First Annual Rutgers Society of Women Engineers Graduate Research Symposium.

Dr. O'Carroll will be featured on the front cover of the up-coming Rutgers SoE Magazine (link).

Dr. O'Carroll gives and invited seminar in the Department of Chemistry at Lehman College. Thank you to Prof. Jitianu for the invitation!

The paper "Oxidation of Planar and Plasmonic Ag Surfaces by Exposure to O2/Ar Plasma for Organic Optoelectronic Applications" by Petoukhoff et al. has been accepted for publication in MRS Advances.

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:
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.
Nanoporous Silver Thin Films: Multifunctional Platforms for Influencing Chain Morphology and Optical Properties of Conjugated Polymers
Z. Shen, D. M. O'Carroll, Adv. Funct. Mater. 25, 3302-3313 (2015).

Abstract: Disordered nanoporous silver (NPAg) thin films fabricated by a thermally assisted dewetting method are employed as a platform to influence chain alignment, morphology, and optical properties of three well-known conjugated polymers. Grazing-incidence wide-angle X-ray scattering measurements show that the porous structure of the metal induces close π–π stacking of P3HT chains and extended, planar chain conformations of PFO and F8BT. A greater degree of vertically-oriented P3HT chains are found on NPAg compared with planar Ag. However, PFO and F8BT chain alignment is only affected when pore size is large. The optical properties of NPAg films are investigated by transmission and back-scattering spectroscopies. Strong back-scattering is observed for all NPAg morphologies, especially for NPAg with small pore sizes. Photoluminescence spectroscopy of conjugated polymer layers on NPAg showed pronounced emission enhancements (up to factors of 26) relative to layers on glass. The enhancements are attributed primarily to: 1) redistribution of conjugated polymer emission by Ag; 2) redirection of emission by polymer-filled nanopores; and 3) local electromagnetic field effects. This work demonstrates the potential of NPAg-thin films to influence molecular chain morphology and to improve light-extraction in organic optoelectronic devices.
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Plasmonic Electrodes for Bulk-Heterojunction Organic Photovoltaics: A Review
C. E. Petoukhoff, Z. Shen, M. Jain, A. Chang, D. M. O'Carroll, J. Photon. Energy, 5, 057002-1-28 (2015).

We review recent progress on the integration of plasmonic electrodes into bulk-heterojunction organic photovoltaic devices. Plasmonic electrodes, consisting of thin films of metallic nanostructures, can exhibit a number of optical, electrical, and morphological effects that can be exploited to improve performance parameters of ultrathin photovoltaic active layers. We review the various types of plasmonic electrodes that have been incorporated into organic photovoltaics such as nanohole, nanowire, and nanoparticle arrays and grating electrodes and their impact on various device performance parameters. The use of plasmonic back electrodes can impact device performance in a number of ways because the mechanisms of performance improvements are often a complex combination of optical, electrical, and structural effects. Inverted bulk heterojunction device architectures have been shown to benefit from the multifunctionality of plasmonic back electrodes as they can minimize space-charge effects and reduce hole carrier collection lengths in addition to providing improved light localization in the active layer. The use of semi-transparent plasmonic electrodes can also be beneficial for organic photovoltaics as they can exhibit a variety of optical properties such as light scattering, light localization, extraordinary transmission of light, and absorption-induced transparency, in addition to providing an alternative to metal oxide–based transparent electrodes.