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Search Publications by: Sebastian Engmann (Assoc)

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Displaying 1 - 24 of 24

Magnetic Field Sensor Based on a OLED/Organic Photodetector Stack

August 1, 2023
Author(s)
Sebastian Engmann, Emily Bittle, David Gundlach
In this study a novel, all organic magnetic field sensor is presented based on an organic light emitting diode (OLED) and organic photodetector (OPD) with a maximum field sensitivity comparable to commercial Hall-sensors. The sensor function is driven by

Resolving Complex Photoconductivity of Perovskite and Organic Semiconductor Films Using Phase-Sensitive Microwave Interferometry

March 2, 2023
Author(s)
Jasleen Bindra, Pragya Shrestha, Sebastian Engmann, Chad Cruz, Lea Nienhaus, Emily Bittle, Jason Campbell
Complex transient photoconductivity (Δσ) contains rich fingerprints of charge recombination dynamics in photoactive films. However, a direct measure of both real (Δσ′) and imaginary (Δσ″) components has proven difficult using conventional cavity-based time

The role of orientation in the MEL response of OLEDs

July 13, 2021
Author(s)
Sebastian Engmann, Emily Bittle, Lee J. Richter, Rawad Hallani, John Anthony, David J. Gundlach
Magneto electroluminescence (MEL) is emerging as a powerful tool for the study of spin dynamics in emitting devices. The shape of the MEL response is typically used to draw qualitative inference on the dominant process (singlet fission or triplet fusion)

Synergistic effect of carotenoid and silicone-based additives for photooxidatively stable organic solar cells with enhanced elasticity

July 7, 2021
Author(s)
Michela Prete, Elisa Ogliani, Mikkel Bregnhoj, Subham Dastidar, Jonas Lissau, Horst-Gunter Rubahn, Sebastian Engmann, Anne Ladegaard Skov, Michael Brook, Peter Ogilby, Adam Printz, Vida Turkovic, Morten Madsen
Photochemical and mechanical stability are critical factors in the production and application of organic solar cells. While these factors can individually be improved using different additives, there is no example of studies on the combined effects of such

Polarization Dependence of Charge Conduction in Conjugated Polymer Films Investigated with Time- Resolved Terahertz Spectroscopy

March 6, 2020
Author(s)
Timothy J. Magnanelli, Sebastian Engmann, Jared K. Wahlstrand, John C. Stephenson, Lee J. Richter, Edwin J. Heilweil
We interrogate polarization anisotropy associated with charge conduction in films of the block co polymer PCDTPT, consisting of alternating cyclopenta dithiophene (donor) and thiadiazolo pyridine (acceptor) units with respect to sample morphology. Film

Biomimetic Approach to Inhibition of Photooxidation in Organic Solar Cells Using Beta-Carotene as an Additive

October 14, 2019
Author(s)
Sebastian Engmann, Vida Turkovic, Michela Prete, Mikkel Bregnhoj, Liana Inasaridze, Dmytro Volyniuk, Filipp Obrezkov, Juozas V. Grazulevicius, Horst G. Rubahn, Pavel Troshin, Peter R. Ogilby, M. Madsen
Recent improvements in the power conversion efficiencies of organic photovoltaic (OPV) cells have highlighted the fact that OPV device lifetimes are now the main bottleneck for further advances of this technology. As such, understanding and controlling

Morphology of a thermally stable small molecule OPV blend comprising a liquid crystalline donor and fullerene acceptor

June 4, 2019
Author(s)
Alexander J. Bourque, Sebastian Engmann, Allison Fuster, Chad R. Snyder, Lee J. Richter, Paul B. Geraghty, David J. Jones
Recently organic photovoltaic (OPV) devices comprising the small molecule liquid-crystalline donor, benzodithiophene-quaterthiophene-rhodanine (BQR), were demonstrated to achieve high performance when thermally processed, avoiding the need for slow-drying

Higher Order Effects in Organic LEDs with Sub-bandgap Turn-on

January 16, 2019
Author(s)
Sebastian Engmann, Adam J. Barito, Emily Bittle, Chris Giebink, Lee J. Richter, David J. Gundlach
Spin-dependent nonlinear processes in organic materials such as singlet-fission and triplet- triplet annihilation could increase the performance for photovoltaics, detectors, and light emitting diodes. Rubrene/C60 light emitting diodes exhibit a distinct

Characterization of Interfacial Structure in Polymer-Fullerene Bulk Heterojunctions via 13C {2H} Rotational Echo Double Resonance NMR

July 13, 2018
Author(s)
Ryan C. Nieuwendaal, Dean M. DeLongchamp, Martin Heeney, Jan Hummelen, Chad R. Snyder, Ronald L. Jones, Sebastian Engmann, Lee J. Richter, Zhuping Fei, Alex Sieval
We introduce a new application of solid state NMR measurements towards characterizing the donor-acceptor interfaces within bulk heterojunction (BHJ) films. Rotational echo double resonance (REDOR) is used to measure dipolar couplings between 13C nuclei on

Simple Transfer from Spin Coating to Blade Coating Through Processing Aggregated Solutions

September 22, 2017
Author(s)
Jeff L. Hernandez, Nabankur Deb, Rylan M. Wolfe, Chi K. Lo, Sebastian Engmann, Lee J. Richter, John R. Reynolds
To develop an understanding of the effect spin coating or blade coating have on the morphology of polymer:fullerene thin films for organic solar cells, we have investigated the morphology of poly[5-(2-hexyldecyl)-1,3-thieno[3,4-c]pyrrole-4,6-dione-alt-5,5-

The dependence of electrical performance on structural organization in low mobility polymer field effect transistors

April 16, 2017
Author(s)
Emily G. Bittle, Hyun W. Ro, Chad R. Snyder, Sebastian Engmann, Regis J. Kline, Oana Jurchescu, Dean M. DeLongchamp, David J. Gundlach
Polymer semiconductors are contenders for use in printed, flexible electronics. Though organic electronic materials have been studied for many years, the physics of charge transport is still under investigation. This is in part due to the large variability

Reduced Bimolecular Recombination in Blade-Coated, High-Efficiency, Small-Molecule Solar Cells

March 22, 2017
Author(s)
Sebastian Engmann, Hyun W. Ro, Andrew A. Herzing, Dean M. DeLongchamp, Chad R. Snyder, Lee J. Richter, Adam J. Barito, David J. Gundlach
The full benefit of emerging solution deposited photovoltaic devices requires development of processes compatible with high speed manufacturing. Extensive studies of the lab-to-fab challenge have been performed on polymer donor based organic photovoltaics

In situ X-ray scattering studies of the influence of an additive on the formation of a low-bandgap bulk- heterojunction

February 21, 2017
Author(s)
Felicia A. Bokel, Lee J. Richter, Sebastian Engmann, Andrew Herzing, Brian A. Collins, Hyun W. Ro, Dean DeLongchamp
The evolution of the morphology of a high-efficiency, blade-coated, organic-photovoltaic (OPV) active layer containing the low band-gap polymer poly[(4,8-bis[5-(2-ethylhexyl)thiophene-2-yl]benzo[1,2-b:4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)

Film morphology evolution during solvent vapor annealing of highly efficient small molecule donor/acceptor blends

September 15, 2016
Author(s)
Sebastian Engmann, Hyun W. Ro, Andrew Herzing, Chad R. Snyder, Lee J. Richter, Paul Geraghty, David Jones
Solution-processable small molecule photovoltaics based on the novel molecular donor, benzodithiophene terthiophene rhodamine (BTR), recently have shown maximum power conversion efficiencies above 8% for active layer thicknesses up to 400 nm, using post

Morphology-insensitive Performance Facilitates Transition from Spin-Coating to Roll-to-Roll Coating For High-Performance, Solution-Processed Solar Cells

August 2, 2016
Author(s)
Lee J. Richter, Jonathan Downing, Sebastian Engmann, Hyun W. Ro, Andrew A. Herzing, Dean M. DeLongchamp, Subhrangsu Mukherjee, Harald Ade, Maged Addelsamie, Aram Amassian, Yuhang Liu, He Yan
Solution processing via roll-to-roll (R2R) coating promises a low cost, low thermal-budget, sustainable revolution for the production of solar cells. Yet virtually all high performance solution processed research cells have been demonstrated by spin

Real-time Photoluminescence Studies of Thin Film Formation in Organic Solar Cells

February 29, 2016
Author(s)
Sebastian Engmann, Felicia A. Bokel, Hyun W. Ro, Dean M. DeLongchamp, Lee J. Richter
We present a method to study the structural evolution of organic bulk-heterojunctions via real-time, in-situ, steady state photoluminescence (PL). In-situ PL, in combination with real-time transmission and reflection measurements, allowed us to

Real-time x-ray scattering studies of film formation in high performing small-molecule organic solar cells

May 23, 2015
Author(s)
Sebastian Engmann, Felicia A. Bokel, Andrew Herzing, Hyun W. Ro, Dean DeLongchamp, Lee J. Richter, Claudio Girotto, Bruno Caputo
We have studied the influence of the additive diiodoctane on the formation dynamics of high performance bulk heterojunction (BHJ) films based the small molecule donor 7,7'-(4,4bis(2- ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-5-(5

In-situ morphology studies of the mechanism for solution additive effects on the formation of bulk heterojunction films.

September 29, 2014
Author(s)
Lee J. Richter, Dean M. DeLongchamp, Kang W. Chou, Aram Amassian, A Hexemer, Eric Schaible, Felicia A. Bokel, Sebastian Engmann
The most successful active film morphology in organic photovoltaics is the bulk heterojunction (BHJ). The performance of a BHJ arises from a complex interplay of the spatial organization of the segregated donor and acceptor phases and the local order