128 research outputs found
Solution Processed Organic Solar Cells Based on Fullerene and Non-Fullerene Acceptors
No full textOrganic solar cells (OSCs) can lead to innovative niche photovoltaic applications due to their unique,
distinguishing properties compared to traditional solar cell technologies such as low weight, flexibility,
esthetic possibilities and large area production through solution processing. In this dissertation the
focus is on solution-processed OSCs based on fullerene and non-fullerene acceptors, by investigating a
broad variety of novel conjugated polymers. First of all, three random terpolymers (P1, P2, and P3)
with donor–acceptor–donor–acceptor molecular configuration, comprising fluorinated benzotriazole
(FTAZ) and thienothiophene-capped diketopyrrolopyrrole (TTDPP) as the first and second electronaccepting moieties and thienyl-substituted benzodithiophene (BDTT) as the electron-donating unit,
were designed and synthesized. By tuning the ratio of TTDPP and FTAZ, the optoelectronic properties
of the terpolymers were systematically varied. All materials exhibited a broad absorption window
spanning from 300 to 900 nm, illustrating the success of the terpolymer approach. Fullerene-based
OSCs fabricated from the terpolymer with the highest content of TTDPP (P1) afforded a power
conversion efficiency (PCEs) of 5.7%, with a short-circuit current density (Jsc) of 15.2 mA cm–2
. On
the other hand, solar cell devices composed of the terpolymer with the lowest content of TTDPP (P3)
and the narrow gap non-fullerene acceptor IEICO-4F exhibited a higher efficiency of 6.3%, with an
enhanced Jsc of 17.6 mA cm–2
, as a result of a better complementarity in the absorption of the donor
and acceptor materials and well-balanced charge carrier mobilities. This efficiency represented the
best value for non-fullerene OSCs based on DPP-containing polymers at the time of publication of this
work.
In the next phase, donor copolymers P4, P5, and P6, based on 2H-benzo[d][1,2,3]triazole-5,6-
dicarboxylic imide, were studied. Both fullerene and non-fullerene OSCs were prepared and
characterized. The fullerene-based OSCs fabricated using 3% 1-chloronaphthalene (CN) as a solvent
additive afforded PCEs of 7.6, 7.2, and 7.2% for P4, P5, and P6, respectively, with enhanced hole
and electron mobilities. Furthermore, non-fullerene devices with an inverted device architecture were
also fabricated in combination with ITIC, affording PCEs of 8.4, 6.4, and 7.6%, respectively, by
controlling the morphology of the active layer with 1,8-diiodooctane (DIO) as a solvent additive and
thermal annealing at 120 °C. Inspired by the results obtained, we further extended our investigation
toward intrinsically stable OSCs through studying the in-situ intrinsic thermal window of operation
(from 30 to 180 °C) for both conventional and inverted type devices. It was found that both the
fullerene and non-fullerene OSCs functioned well over a large thermal window with excellent thermal
stability.
In another part of the dissertation, the effect of side chain variations on the photophysical,
morphological and photovoltaic properties of two novel high gap donor polymers P7 and P8 in
combination with both fullerene and non-fullerene acceptors were investigated. P7 showed a deeper
highest occupied molecular orbital (HOMO) energy level, which resulted in higher open-circuit voltages (Voc). Nevertheless, the polymer solar cells fabricated using P8 in combination with PC71BM afforded a
higher PCE of 7.3% (vs 4.0% for P7:PC71BM). By using the non-fullerene acceptor ITIC, better device
efficiencies of 6.9% and 9.6% for P7:ITIC and P8:ITIC, respectively, were achieved. The better
performance of P8:ITIC is attributed to the broad absorption, balanced charge transport and favorable
blend morphology, and is among the best TzBI-containing non-fullerene solar cells.
Furthermore, two push-pull type high band gap conjugated polymers P9 and P10, based on the
ladder-type donor unit indacenodithieno[3,2-b]thiophene (IDTT) and bithiazole (BTz) as the acceptor
component were studied. The polymers exhibited relatively high optical gaps of ~2.0 eV with strong
absorption in the range of 400 to 600 nm. Electrochemical investigations indicated a lower HOMO
energy level (–5.58 eV) for P10 as compared to P9 (–5.46 eV), enabling to achieve a higher Voc. The
PCE of 5.1% achieved from solar cells based on P9:PC71BM blend was higher than those obtained
from P10:PC71BM (4.6%) blend.
The photovoltaic performances of five benzotriazole (BTZ)-based conjugated copolymers P11–P15
were also investigated. The polymers showed high thermal stability and HOMO energy levels from
–5.33 to –5.40 eV. Due to the deep HOMO level of P13, the Voc of the device improved to 0.88 V. The
PCEs of the devices were all in the range from 1.8 to 2.1%.
Finally, a series of low-HOMO level conjugated copolymers P16–P22, based on
pyrrolobenzothiadiazoledione, pyrrolobenzotriazoledione, and benzothiadiazole were studied for
organic photovoltaic applications. The OSCs fabricated from P16–P22 afforded a PCE from 1.0% to
3.8% with a high Voc up to 1.06 V. Furthermore, some low band gap copolymers P23–P30 with
extended absorption ≥ 1000 nm were also investigated in OSCs. They afforded very low PCEs from
0.02% to 0.5%. However, such low band gap polymers with broad spectral response from 300 to
1500 nm and different bands in the ultraviolet and near-infrared (NIR) range may be interesting for
NIR photodetector applications. Non-fullerene OSCs based on indacenodithienothiophene-altbenzothiadiazole copolymers P31 and P32 were then fabricated as well. The best PCE obtained was
1.0%, with a relatively high Voc of 0.96 V for P32:ITIC. Furthermore, all-polymer solar cells were also
fabricated from a 2H-benzo[d][1,2,3]triazole-5,6-dicarboxylic imide donor polymer and naphthalene
diimide-based acceptor polymers P33 and P34. The best PCE achieved was 1.7% for P4:P34-based
devices
Solution Processed Organic Solar Cells Based on Fullerene and Non-Fullerene Acceptors
No full textOrganic solar cells (OSCs) can lead to innovative niche photovoltaic applications due to their unique,
distinguishing properties compared to traditional solar cell technologies such as low weight, flexibility,
esthetic possibilities and large area production through solution processing. In this dissertation the
focus is on solution-processed OSCs based on fullerene and non-fullerene acceptors, by investigating a
broad variety of novel conjugated polymers. First of all, three random terpolymers (P1, P2, and P3)
with donor–acceptor–donor–acceptor molecular configuration, comprising fluorinated benzotriazole
(FTAZ) and thienothiophene-capped diketopyrrolopyrrole (TTDPP) as the first and second electronaccepting moieties and thienyl-substituted benzodithiophene (BDTT) as the electron-donating unit,
were designed and synthesized. By tuning the ratio of TTDPP and FTAZ, the optoelectronic properties
of the terpolymers were systematically varied. All materials exhibited a broad absorption window
spanning from 300 to 900 nm, illustrating the success of the terpolymer approach. Fullerene-based
OSCs fabricated from the terpolymer with the highest content of TTDPP (P1) afforded a power
conversion efficiency (PCEs) of 5.7%, with a short-circuit current density (Jsc) of 15.2 mA cm–2
. On
the other hand, solar cell devices composed of the terpolymer with the lowest content of TTDPP (P3)
and the narrow gap non-fullerene acceptor IEICO-4F exhibited a higher efficiency of 6.3%, with an
enhanced Jsc of 17.6 mA cm–2
, as a result of a better complementarity in the absorption of the donor
and acceptor materials and well-balanced charge carrier mobilities. This efficiency represented the
best value for non-fullerene OSCs based on DPP-containing polymers at the time of publication of this
work.
In the next phase, donor copolymers P4, P5, and P6, based on 2H-benzo[d][1,2,3]triazole-5,6-
dicarboxylic imide, were studied. Both fullerene and non-fullerene OSCs were prepared and
characterized. The fullerene-based OSCs fabricated using 3% 1-chloronaphthalene (CN) as a solvent
additive afforded PCEs of 7.6, 7.2, and 7.2% for P4, P5, and P6, respectively, with enhanced hole
and electron mobilities. Furthermore, non-fullerene devices with an inverted device architecture were
also fabricated in combination with ITIC, affording PCEs of 8.4, 6.4, and 7.6%, respectively, by
controlling the morphology of the active layer with 1,8-diiodooctane (DIO) as a solvent additive and
thermal annealing at 120 °C. Inspired by the results obtained, we further extended our investigation
toward intrinsically stable OSCs through studying the in-situ intrinsic thermal window of operation
(from 30 to 180 °C) for both conventional and inverted type devices. It was found that both the
fullerene and non-fullerene OSCs functioned well over a large thermal window with excellent thermal
stability.
In another part of the dissertation, the effect of side chain variations on the photophysical,
morphological and photovoltaic properties of two novel high gap donor polymers P7 and P8 in
combination with both fullerene and non-fullerene acceptors were investigated. P7 showed a deeper
highest occupied molecular orbital (HOMO) energy level, which resulted in higher open-circuit voltages (Voc). Nevertheless, the polymer solar cells fabricated using P8 in combination with PC71BM afforded a
higher PCE of 7.3% (vs 4.0% for P7:PC71BM). By using the non-fullerene acceptor ITIC, better device
efficiencies of 6.9% and 9.6% for P7:ITIC and P8:ITIC, respectively, were achieved. The better
performance of P8:ITIC is attributed to the broad absorption, balanced charge transport and favorable
blend morphology, and is among the best TzBI-containing non-fullerene solar cells.
Furthermore, two push-pull type high band gap conjugated polymers P9 and P10, based on the
ladder-type donor unit indacenodithieno[3,2-b]thiophene (IDTT) and bithiazole (BTz) as the acceptor
component were studied. The polymers exhibited relatively high optical gaps of ~2.0 eV with strong
absorption in the range of 400 to 600 nm. Electrochemical investigations indicated a lower HOMO
energy level (–5.58 eV) for P10 as compared to P9 (–5.46 eV), enabling to achieve a higher Voc. The
PCE of 5.1% achieved from solar cells based on P9:PC71BM blend was higher than those obtained
from P10:PC71BM (4.6%) blend.
The photovoltaic performances of five benzotriazole (BTZ)-based conjugated copolymers P11–P15
were also investigated. The polymers showed high thermal stability and HOMO energy levels from
–5.33 to –5.40 eV. Due to the deep HOMO level of P13, the Voc of the device improved to 0.88 V. The
PCEs of the devices were all in the range from 1.8 to 2.1%.
Finally, a series of low-HOMO level conjugated copolymers P16–P22, based on
pyrrolobenzothiadiazoledione, pyrrolobenzotriazoledione, and benzothiadiazole were studied for
organic photovoltaic applications. The OSCs fabricated from P16–P22 afforded a PCE from 1.0% to
3.8% with a high Voc up to 1.06 V. Furthermore, some low band gap copolymers P23–P30 with
extended absorption ≥ 1000 nm were also investigated in OSCs. They afforded very low PCEs from
0.02% to 0.5%. However, such low band gap polymers with broad spectral response from 300 to
1500 nm and different bands in the ultraviolet and near-infrared (NIR) range may be interesting for
NIR photodetector applications. Non-fullerene OSCs based on indacenodithienothiophene-altbenzothiadiazole copolymers P31 and P32 were then fabricated as well. The best PCE obtained was
1.0%, with a relatively high Voc of 0.96 V for P32:ITIC. Furthermore, all-polymer solar cells were also
fabricated from a 2H-benzo[d][1,2,3]triazole-5,6-dicarboxylic imide donor polymer and naphthalene
diimide-based acceptor polymers P33 and P34. The best PCE achieved was 1.7% for P4:P34-based
devices
Book Review: Slaves of State, Intellectuals of development in Ethiopia: A Genealogy of Development in Ethiopia
No full textSemeneh Ayalew Asfaw
Author: Yonas Ashine Demissie
Title: Slaves of State, Intellectuals of development in Ethiopia: A Genealogy of Development in Ethiopia
Makerere Institute of Social Research
Printed by Chrome Partner
Study of EC Mechanism by Cyclic Voltammetry: Electrochemical Oxidation of Catechol in the Presence of Imidazole
No full textElectrochemical oxidation of catechol has been studied in the presence of imidazole as
nucleophile in aqueous solution, using cyclic voltammetry. The results indicate the
participation of catechol in 1, 4- Michael reaction with imidazole to form the corresponding
catechol thioethers. Based on the observed EC mechanism, the homogeneous rate constants
(kfcal) of the reaction of o-benzoquinone with imidazole were estimated by fitting the
theoretical working curve with the experimental working curve
Diketopyrrolopyrrole-based terpolymers with tunable broad band absorption for fullerene and fullerene-free polymer solar cells
No full textA series of random terpolymers with donor-acceptor-donor-acceptor molecular configuration, comprising fluorinated benzotriazole (FTAZ) and thienothiophene-capped diketopyrrolopyrrole (TTDPP) as the first and second electron-accepting moieties and thienyl-substituted benzodithiophene (BDTT) as the electron-donating unit, are designed for polymer solar cells. By tuning the ratio of TTDPP and FTAZ, the optoelectronic properties of the terpolymers are systematically varied. All materials exhibit a broad absorption window spanning from 300 to 900 nm, illustrating the success of the terpolymer approach. Fullerene-based polymer solar cells fabricated from the terpolymer with the highest content of TTDPP afford a power conversion efficiency of 5.7%, with a short-circuit current density of 15.2 mA cm -2 . On the other hand, solar cell devices composed of the terpolymer with the lowest content of TTDPP and the narrow gap non-fullerene acceptor IEICO-4F exhibit a higher efficiency of 6.3%, with an enhanced short-circuit current density of 17.5 mA cm -2 , as a result of a better complementarity in the absorption of the donor and acceptor materials and well-balanced charge carrier mobilities. This efficiency represents the best value for fullerene-free polymer solar cells based on DPP-containing polymers to date
A Compartmentalized Mathematical Models of Normal and Failing Mouse Cardiac Myocytes
No full textAtrial fibrillations and heart failure are among the leading cardiovascular diseases in the world. Understanding the development and progression of these diseases requires a thorough knowledge of the electrophysiological mechanisms in a healthy and diseased cardiac myocyte. This goal can be achieved by using mathematical modeling along with experimental investigations. Here, we developed two new comprehensive mathematical models of the mouse atrial and ventricular myocytes. The first one is a novel compartmentalized mathematical model of mouse atrial myocytes. This model combines the action potential, [Ca2+]i dynamics, and β-adrenergic signaling cascade for a subpopulation of right atrial myocytes with a developed transverse-axial tubule system. The model consists of three compartments related to β-adrenergic signaling (caveolae, extracaveolae, and cytosol) and employs local control of Ca2+-release. It also simulates the mechanisms of action potential generation and describes atrial-specific Ca2+ handling and frequency dependences of the action potential and [Ca2+]i transients. The model showed that the T-type Ca2+ current significantly affects the later stage of the action potential with little effect on [Ca2+]i transients. Blocking the small-conductance Ca2+-activated K+ current leads to the prolongation of the action potential at high intracellular Ca2+ concentrations. Simulation results obtained from the atrial cell model were compared to those from ventricular myocytes. The developed model presents a valuable tool for studying complex electrical properties in the mouse atria and could be applied to understand atrial physiology and arrhythmogenesis. The second model is a novel compartmentalized mathematical model of failing mouse ventricular myocytes after TAC procedure. The model effectively describes the cell geometry, action potentials, [Ca2+]i transients, and β1- and β2-adrenergic signaling in the failing cells. Simulation results obtained from a failing cells’ model were compared to those from the normal ventricular myocytes. Exploration of the model revealed the sarcoplasmic reticulum Ca2+ load mechanisms in failing ventricular myocytes. We also described a proarrhythmic behavior of Ca2+ dynamics upon stimulation with isoproterenol and mechanisms of the proarrhythmic behavior suppression. The developed model can be used to explain the existing experimental data on failing mouse ventricular myocytes and make experimentally testable predictions of the failing myocyte behavior.Doctor of Philosophy (PhD)Mathematics and Statistic
Author Correction: A Peptoid Delivers CoQ-derivative to Plant Mitochondria via Endocytosis
No full textAn amendment to this paper has been published and can be accessed via a link at the top of the paper
Exploring the High‐Temperature Window of Operation for Organic Photovoltaics: A Combined Experimental and Simulations Study
No full textThe global climate change negatively affects the photovoltaic performance of traditional solar cell technologies. This article investigates the potential of organic photovoltaics (OPV) for high-temperature environments, ranging from urban hot summers (30—40\ua0\ub0C) and desert regions (65\ua0\ub0C) up to (aero) space conditions (130\ua0\ub0C), the thermal window in which OPV can operate. The approach is based on a combination of experiments and simulations up to 180\ua0\ub0C, moving significantly beyond the conventional temperature ranges reported in the literature. New 2H-benzo[d][1,2,3]triazole-5,6-dicarboxylic imide-based copolymers with decomposition onset temperatures above 340\ua0\ub0C are used for this study, in combination with non-fullerene acceptors. Contrary to their inorganic counterparts, OPV devices show a positive temperature coefficient up to ≈90\ua0\ub0C. At temperatures of 150\ua0\ub0C, they are still operational, retaining their room temperature efficiency. Complementary simulations are performed using an in-house developed software package that numerically solves the drift-diffusion equations to understand the general trends in the obtained current–voltage characteristics and the materials’ intrinsic behavior as a function of temperature. The presented methodology of combined high-temperature experiments and simulations can be further applied to investigate the thermal window of operation for other OPV material systems, opening novel high-temperature application routes
A study on Contagious Caprine Pleuropneumonia (CCPP) in goats at an export oriented abattoir, Debrezeit, Ethiopia
No full text300 goat serum samples from an export-oriented abattoir were tested for contagious caprine pleuropneumonia antibodies by the complement fixation test. The disease prevalence was 31% with no significant differences (P > 0.05) between the regions “Borena”, “Bale”, “Afar” and “Jinka” or the age of the goats (P > 0.05). Gross pathology and histopathology of the lung primary lesions were indicative of pleuropneumonia caused by Mycoplasma capricolum subsp. capripneumoniae
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