Engineering dielectric constants in organic semiconductors

2017 ◽  
Vol 5 (15) ◽  
pp. 3736-3747 ◽  
Author(s):  
Ardalan Armin ◽  
Dani M. Stoltzfus ◽  
Jenny E. Donaghey ◽  
Andrew J. Clulow ◽  
Ravi Chandra Raju Nagiri ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Organic Semiconductors ◽  
Organic Semiconductor ◽  
Photovoltaic Device ◽  
Dielectric Constants ◽  
Optical Frequency ◽  
Generation Efficiency ◽  
Charge Generation

An optical-frequency dielectric constant of 4.6 leads to improved charge generation efficiency in an organic semiconductor homojunction photovoltaic device.

scholarly journals Photoconversion Mechanism at the pn-Homojunction Interface in Single Organic Semiconductor

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1727 ◽  
Author(s):  
Ji-Hyun Lee ◽  
Armand Perrot ◽  
Masahiro Hiramoto ◽  
Seiichiro Izawa
Keyword(s):  
Organic Semiconductors ◽  
Organic Semiconductor ◽  
Energy Structure ◽  
Free Charge ◽  
Charge Generation ◽  
Recombination Processes ◽  
Single Host ◽  
Donor Acceptor ◽  
Doping Technique ◽  
Determining Factor

Clarifying critical differences in free charge generation and recombination processes between inorganic and organic semiconductors is important for developing efficient organic photoconversion devices such as solar cells (SCs) and photodetector. In this study, we analyzed the dependence of doping concentration on the photoconversion process at the organic pn-homojunction interface in a single organic semiconductor using the temperature dependence of J–V characteristics and energy structure measurements. Even though the organic pn-homojunction SC devices were fabricated using a single host material and the doping technique resembling an inorganic pn-homojunction, the charge generation and recombination mechanisms are similar to that of conventional donor/acceptor (D/A) type organic SCs; that is, the charge separation happens from localized exciton and charge transfer (CT) state being separated by the energy offset between adjacent molecules, and the recombination happens from localized charge carrier at two adjacent molecules. The determining factor for photoconversion processes is the localized nature of charges in organic semiconductors. The results demonstrated that controlling the delocalization of the charges is important to realize efficient organic photoconversion devices.

scholarly journals An effective strategy to enhance the dielectric constant of organic semiconductors – CPDTTPD-based low bandgap polymers bearing oligo(ethylene glycol) side chains

2018 ◽  
Vol 6 (3) ◽  
pp. 500-511 ◽  
Author(s):  
Jeroen Brebels ◽  
Evgenia Douvogianni ◽  
Dries Devisscher ◽  
Raghavendran Thiruvallur Eachambadi ◽  
Jean Manca ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Organic Semiconductors ◽  
Dielectric Constants ◽  
Side Chains ◽  
Effective Strategy ◽  
Low Bandgap

Gradually increasing dielectric constants (up to 6.3) are obtained for a series of PCPDTTPD polymers.

Origin of charge generation efficiency of metal oxide p-dopants in organic semiconductors

2011 ◽  
Vol 12 (6) ◽  
pp. 950-954 ◽  
Author(s):  
Jae-Hyun Lee ◽  
Hyun-Mi Kim ◽  
Ki-Bum Kim ◽  
Jang-Joo Kim
Keyword(s):  
Metal Oxide ◽  
Organic Semiconductors ◽  
Generation Efficiency ◽  
Charge Generation

scholarly journals Rational Design of Donor Acceptor Based Semiconducting Copolymers with High Dielectric Constant

2020 ◽  
Author(s):  
Aiswarya Abhisek Mohapatra ◽  
Yifan Dong ◽  
Puttaraju Boregowda ◽  
Ashutosh Mohanty ◽  
Aditya Sadhanala ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Rational Design ◽  
Dielectric Constants ◽  
Side Chains ◽  
Free Charge ◽  
Coulombic Interaction ◽  
Polymer Backbone ◽  
Donor Acceptor

<div> <div> <div> <p>An efficient photogeneration of free charge carriers has long been recognized as the paramount challenge in organic photovoltaic (OPV) devices. The low dielectric constant organic semiconductors fall short to reduce strong Coulombic interaction of tightly bound exciton and hence lead to a loss mechanism in OPVs due to charge-carrier recombination. To circumvent this problem, we adopt a strategy to enhance the dielectric constant of organic semiconductors by incorporating tetraethyleneglycol (TEG) side-chains. We report synthesis of three new semiconducting copolymers by combining thiophene substituted diketopyrrolopyrrole (TDPP) monomer with three other monomeric units with varying electron donating strength: benzodithiophene (BBT-3TEG-TDPP), TDPP (TDPP-3TEG-TDPP) and naphthalene diimide (PNDITEG-TDPP). BBT-3TEG-TDPP and PNDITEG-TDPP showed highest dielectric constants (~ 5) at 1MHz frequency suggesting efficient contribution of dipolar polarization from TEG side-chains. To understand the electronic contribution of the polymer backbone and the polarity of TEG side-chains, and the resulting enhancement of the dielectric constant, we further performed first-principles density functional theory calculations. Single-component organic solar cells (OSC) fabricated utilizing these polymers resulted in poor performance which is attributed to the absence of free charge generation. Furthermore, transient absorption spectroscopy studies show low exciton diffusion length as observed in donor-acceptor type conjugated polymers. Our results suggest that, the strategy of enhancing dielectric constant with polar side-chains is not sufficient to reduce Coulombic interaction between hole and electron in OSCs. </p> </div> </div> </div>

scholarly journals Free Charge Photogeneration in a Single Component High Photovoltaic Efficiency Organic Semiconductor

2021 ◽  
Author(s):  
Justin Hodgkiss ◽  
Michael Price ◽  
Paul Hume ◽  
Aleksandra Ilina ◽  
Isabella Wagner ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Organic Photovoltaics ◽  
Photovoltaic Cells ◽  
Single Component ◽  
Dielectric Constants ◽  
Organic Photovoltaic ◽  
Free Charge ◽  
Photovoltaic Devices ◽  
Organic Photovoltaic Devices ◽  
Charge Generation

Abstract Organic photovoltaic cells promise cheap, flexible and scalable solar energy. Whereas light directly generates free charges in silicon photovoltaic cells, bound electron and hole pairs known as excitons are understood to be the primary excitations in organic semiconductors due to their low dielectric constants. These excitons must then be split apart at molecular heterojunctions in order to extract current. Recent record efficiency organic photovoltaics utilise the small molecule, Y6, as a key component in the photon-absorbing blend layer. This molecule and its analogues – unlike previous organic semiconductors – have both low band-gaps and high dielectric constants. Here we show that, in a neat film of Y6, these factors lead to intrinsic free charge generation without the need for a molecular heterojunction to split the exciton. We use a suite of intensity-dependent optical spectroscopy measurements to show that a significant (20-90%) fraction of free charges exist in equilibrium with bound states at light intensity equivalent to 1 sun. Rapid bimolecular charge recombination constrains single component Y6 organic photovoltaic devices to low efficiencies, but this recombination is reduced by the introduction of small quantities of donor polymer. Quantum-chemical calculations reveal charge generation pathways through strong coupling between exciton and CT states, and an intermolecular polarisation pattern that drives exciton dissociation. Our results challenge the understanding of how current record efficiency organic photovoltaics operate, and point towards new future possibilities – offering a molecular picture of intrinsic charge generation as a platform to improve charge yields, and renewing the possibility of efficient single-component organic photovoltaic devices.

scholarly journals Rational Design of Donor Acceptor Based Semiconducting Copolymers with High Dielectric Constant

2020 ◽  
Author(s):  
Aiswarya Abhisek Mohapatra ◽  
Yifan Dong ◽  
Puttaraju Boregowda ◽  
Ashutosh Mohanty ◽  
Aditya Sadhanala ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Rational Design ◽  
Dielectric Constants ◽  
Side Chains ◽  
Free Charge ◽  
Coulombic Interaction ◽  
Polymer Backbone ◽  
Donor Acceptor

<div> <div> <div> <p>An efficient photogeneration of free charge carriers has long been recognized as the paramount challenge in organic photovoltaic (OPV) devices. The low dielectric constant organic semiconductors fall short to reduce strong Coulombic interaction of tightly bound exciton and hence lead to a loss mechanism in OPVs due to charge-carrier recombination. To circumvent this problem, we adopt a strategy to enhance the dielectric constant of organic semiconductors by incorporating tetraethyleneglycol (TEG) side-chains. We report synthesis of three new semiconducting copolymers by combining thiophene substituted diketopyrrolopyrrole (TDPP) monomer with three other monomeric units with varying electron donating strength: benzodithiophene (BBT-3TEG-TDPP), TDPP (TDPP-3TEG-TDPP) and naphthalene diimide (PNDITEG-TDPP). BBT-3TEG-TDPP and PNDITEG-TDPP showed highest dielectric constants (~ 5) at 1MHz frequency suggesting efficient contribution of dipolar polarization from TEG side-chains. To understand the electronic contribution of the polymer backbone and the polarity of TEG side-chains, and the resulting enhancement of the dielectric constant, we further performed first-principles density functional theory calculations. Single-component organic solar cells (OSC) fabricated utilizing these polymers resulted in poor performance which is attributed to the absence of free charge generation. Furthermore, transient absorption spectroscopy studies show low exciton diffusion length as observed in donor-acceptor type conjugated polymers. Our results suggest that, the strategy of enhancing dielectric constant with polar side-chains is not sufficient to reduce Coulombic interaction between hole and electron in OSCs. </p> </div> </div> </div>

Homogeneous dispersion of organic p-dopants in an organic semiconductor as an origin of high charge generation efficiency

2011 ◽  
Vol 98 (17) ◽  
pp. 173303 ◽  
Author(s):  
Jae-Hyun Lee ◽  
Hyun-Mi Kim ◽  
Ki-Bum Kim ◽  
Ryota Kabe ◽  
Pavel Anzenbacher ◽  
...  
Keyword(s):  
Organic Semiconductor ◽  
Organic P ◽  
Generation Efficiency ◽  
Charge Generation ◽  
High Charge ◽  
Homogeneous Dispersion

Charge Generation Efficiency of Electrically Doped Organic Semiconductors

2021 ◽  
pp. 100709
Author(s):  
Gunel Huseynova ◽  
Jonghee Lee ◽  
Jeong-Hwan Lee ◽  
Jae-Hyun Lee
Keyword(s):  
Organic Semiconductors ◽  
Generation Efficiency ◽  
Charge Generation
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