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Acceptor Interfaces (acceptor + interface)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Design of Multilayered Nanostructures and Donor,Acceptor Interfaces in Solution-Processed Thin-Film Organic Solar Cells,

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2008
Hiroaki Benten
Abstract Multilayered polymer thin-film solar cells have been fabricated by wet processes such as spin-coating and layer-by-layer deposition. Hole- and electron-transporting layers were prepared by spin-coating with poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) (PEDOT:PSS) and fullerene (C60), respectively. The light-harvesting layer of poly-(p -phenylenevinylene) (PPV) was fabricated by layer-by-layer deposition of the PPV precursor cation and poly(sodium 4-styrenesulfonate) (PSS). The layer-by-layer technique enables us to control the layer thickness with nanometer precision and select the interfacial material at the donor,acceptor heterojunction. Optimizing the layered nanostructures, we obtained the best-performance device with a triple-layered structure of PEDOT:PSS|PPV|C60, where the thickness of the PPV layer was 11,nm, comparable to the diffusion length of the PPV singlet exciton. The external quantum efficiency spectrum was maximum (ca. 20%) around the absorption peak of PPV and the internal quantum efficiency was estimated to be as high as ca. 50% from a saturated photocurrent at a reverse bias of ,3,V. The power conversion efficiency of the triple-layer solar cell was 0.26% under AM1.5G simulated solar illumination with 100,mW,cm,2 in air. [source]

Impact of Ground-State Charge Transfer and Polarization Energy Change on Energy Band Offsets at Donor/Acceptor Interface in Organic Photovoltaics

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Kouki Akaike
Abstract The fullerene (C60)/copper phthalocyanine (CuPc) interface is one of the widely used donor/acceptor (DA) interfaces for organic photovoltaics (OPVs), and information on the electronic structure at the interface is essential for fully understanding the energetics of excitons and carriers in OPVs. Here, an investigation into the energy levels at the C60/CuPc interface is made using UV photoelectron, X-ray photoelectron, and inverse photoemission spectroscopies. The vacuum level and core levels rise with C60 deposition on the CuPc film, which indicates that the interfacial dipole is formed with the negative charge on the C60 side. The interfacial dipole can be formed by the electron transfer from CuPc to C60 in the ground state at the interface, which is indicated by the analysis of the UV,vis,NIR absorption spectrum of the CuPc/C60 blended film. On the other hand, the highest occupied and lowest unoccupied molecular orbitals of CuPc and C60 shift in opposite directions at the interface. This is attributed to the changes of the polarization energies of CuPc and C60 at the interface. The formation of the interfacial dipole and the change of the polarization energy result in the anomalous energy band offsets at the C60/CuPc interface, which are entirely different from those in inorganic p,n junctions. [source]

Triplet Formation in Fullerene Multi-Adduct Blends for Organic Solar Cells and Its Influence on Device Performance

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Clare Dyer-Smith
Abstract In organic solar cells, high open circuit voltages may be obtained by choosing materials with a high offset between the donor highest occupied molecular orbital (HOMO) and acceptor lowest unoccupied molecular orbital (LUMO). However, increasing this energy offset can also lead to photophysical processes that compete with charge separation. In this paper the formation of triplet states is addressed in blends of polyfluorene polymers with a series of PCBM multi-adducts. Specifically, it is demonstrated that the formation of such triplets occurs when the offset energy between donor ionization potential and acceptor electron affinity is ,1.6 eV or greater. Spectroscopic measurements support a mechanism of resonance energy transfer for triplet formation, influenced by the energy levels of the materials, but also demonstrate that the competition between processes at the donor,acceptor interface is strongly influenced by morphology. [source]

Recombination-Limited Photocurrents in Low Bandgap Polymer/Fullerene Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Martijn Lenes
Abstract The charge transport and photogeneration in solar cells based on the low bandgap-conjugated polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H -cyclopenta[2,1-b; 3,4-b,]dithiophene)- alt -4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and fullerenes is studied. The efficiency of the solar cells is limited by a relatively low fill factor, which contradicts the observed good and balanced charge transport in these blends. Intensity dependent measurements display a recombination limited photocurrent, characterized by a square root dependence on effective applied voltage, a linear dependence on light intensity and a constant saturation voltage. Numerical simulations show that the origin of the recombination limited photocurrent stems from the short lifetime of the bound electron-hole pairs at the donor/acceptor interface. [source]

Donor/Spacer/Acceptor Block Copolymer Containing Poly(2,7-carbazole) and Perylenetetracarboxydiimide Subunits

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13 2010
Changduk Yang
Abstract A straightforward synthesis of a conjugated rod/spacer/rod-type block copolymer containing PCz electron-donor and PDI electron-acceptor blocks is described. Two chromophores are covalently connected through sebacate units as saturated spacer. The resulting donor/spacer/acceptor-type block copolymer (PCz-S-PDI) can be applied to limit charge recombination between donor/acceptor interfaces and to control the scale length of nanostructure formation. PCz-S-PDI was used to produce a solar cell with the power conversion efficiency of 0.004%. [source]