Energy level alignment of poly(3-hexylthiophene): [6,6]-phenyl C61 butyric acid methyl ester bulk heterojunction

Xu, Zheng; Chen, Limin; Chen, Mei-Hsin; Li, Gang; Yang, Yang

doi:10.1063/1.3163056

Cited by 148 publications

(146 citation statements)

References 20 publications

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“…5 (flat band condition) and is in excellent agreement with studies obtained on P3HT:PCBM blends on PEDOT-PSS and CsCO 3 contacts [19]. The work function of the PEDOT-PSS substrate is 5.2 eV and the E ICT+ of P3HT is smaller, 4.0 eV, so we expect spontaneous charge transfer at the interface from P3HT to PEDOT-PSS until equilibrium has been reached with the Fermi level becoming pinned to the E ICT+ value.…”

Section: Resultssupporting

confidence: 89%

“…Here, as PCBM is an electron acceptor, the low work function part of the plot is substrate independent (slope = 0), indicating that electronic charge is transferred from the substrate to the PCBM molecules at the interface until the resulting interface dipole brings the Fermi level into equilibrium with the fully relaxed singly occupied molecular orbital of PCBM -. The Φ ORG/SUB energy is ~4.2 eV in this region, which then defines the E ICT-value of PCBM, slightly smaller than the 4.3 eV value obtained in a previous study [19]. For Φ SUB values higher than 4.2 eV, the plot becomes linear with slope = 1 as expected from the vacuum level alignment regime.…”

Section: Resultsmentioning

confidence: 42%

“…Additional information on the technique can be found here [14,15]. The P3HT films were annealed in situ prior to UPS measurement to follow common practice in device fabrication [19,23]. The measurement error in the E ICT+,-values is estimated to be less than ±0.1 eV.…”

Section: Methodsmentioning

confidence: 99%

“…The so-called Integer Charge Transfer model [14][15][16][17] can be used in combination with UPS data to both analyze and predict energy level alignment and charge transfer at the type of weakly-interacting metal-organic and organic-organic interfaces that typically are present in bulk heterojunction solar cells [18,19]. Weakly interacting interfaces are characterized by a negligible hybridization of the π-electronic molecular orbitals and substrate wave functions, which is the case for organic-organic interfaces as well as metal-organic interfaces prepared under ambient atmosphere or low-to high-vacuum conditions [14].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Energy-Level Alignment at Metal–Organic and Organic–Organic Interfaces in Bulk-Heterojunction Solar Cells

Sehati

Lindell

Liu

et al. 2010

IEEE J. Select. Topics Quantum Electron.

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Abstract-Ultraviolet photoelectron spectroscopy measurements in combination with the Integer Charge Transfer model is used to obtain the energy level alignment diagrams for two common types of bulk heterojunction solar cell devices based on poly(3-hexylthiophene) or poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene) as the donor polymer and (6,6)-phenyl-C61-butric-acid as the acceptor molecule. A ground state interface dipole at the donor/acceptor heterojunction is present for both systems but the origin of the interface dipole differs, quadrupole-induced in the case of poly(2-methoxy-5-(3',7'-dimethyl-octyloxy)-1,4-phenylene vinylene) and integer charge transfer state based for poly(3-hexylthiophene). The presence of bound electron-hole charge carriers (charge transfer states) and/or interface dipoles is expected to enhance exciton dissociation into free charge carriers, reducing the probability that the charges become trapped by Coulomb forces at the interface followed by recombination.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 42%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Energy-Level Alignment at Metal–Organic and Organic–Organic Interfaces in Bulk-Heterojunction Solar Cells

Sehati

Lindell

Liu

et al. 2010

IEEE J. Select. Topics Quantum Electron.

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“…Because of the "buried" nature of interfaces in vertical or bulk heterostructures, it has been difficult to study key properties, such as conductivity, dielectric constant, morphology, and surface potential on both sides of the interfaces in the same device. Photoemission spectroscopy technologies (namely, ultraviolet photoemission spectroscopy and its variant, inverse photoemission spectroscopy) have been used to investigate the modulation of orbital energies at such interfaces with good accuracy (10)(11)(12)(13)(14), but not simultaneously with transport measurements.…”

mentioning

confidence: 99%

Field-effect-tuned lateral organic diodes

Dhar

Kini

Xia

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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The operation of organic diodes in solar cells and light-emitting displays strongly depends on the properties of the interfaces between hole- and electron-carrying organic semiconductors. Such interfaces are difficult to characterize, as they are usually buried under the surface or exist as an irregular “bulk heterojunction.” Using a unique fluorinated barrier layer-based lithographic technique, we fabricated a lateral organic p-n junction, allowing the first observation of the potential at an organic p-n interface simultaneously with the charge transport measurements. We find that the diode characteristics of the device (current output and rectification ratio) are consistent with the changes in the surface potentials near the junction, and the current-voltage curves and junction potentials are strongly and self-consistently modulated by a third, gate electrode. The generality of our technique makes this an attractive method to investigate the physics of organic semiconductor junctions. The lithographic technique is applicable to a wide variety of soft material patterns. The observation of built-in potentials makes an important connection between organic junctions and textbook descriptions of inorganic devices. Finally, these kinds of potentials may prove to be controlling factors in charge separation efficiency in organic photovoltaics.

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Formation Mechanism of Fullerene Cation in Bulk Heterojunction Polymer Solar Cells

Yamamoto

Ohkita

Benten

et al. 2012

Adv Funct Materials

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The charge carrier dynamics in blend fi lms of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and conjugated polymers with different ionization potentials are measured using transient absorption spectroscopy to study the formation mechanism of PCBM radical cation, which was previously discovered for blend fi lms of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4phenylenevinylene] (MDMO-PPV) and PCBM. On a nanosecond time scale after photoexcitation, polymer hole polaron and PCBM radical anion are observed but no PCBM radical cation is found in the blends. Subsequently, the fraction of polymer hole polarons decreases and that of PCBM radical cations increases with time. Finally, the fraction of PCBM radical cations becomes constant on a microsecond time scale. The fi nal fraction of PCBM radical cation is dependent on the ionization potential of polymers but independent of the excitation wavelength. These fi ndings show that the formation of PCBM radical cation is due to hole injection from polymer to PCBM domains. Furthermore, the energetic conditions for such hole injection in polymer/PCBM blend fi lms are discussed on the basis of Monte Carlo analysis for hole hopping in a disordered donor/acceptor heterojunction with varying energetic parameters.

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Energy level alignment of poly(3-hexylthiophene): [6,6]-phenyl C61 butyric acid methyl ester bulk heterojunction

Cited by 148 publications

References 20 publications

Energy-Level Alignment at Metal–Organic and Organic–Organic Interfaces in Bulk-Heterojunction Solar Cells

Energy-Level Alignment at Metal–Organic and Organic–Organic Interfaces in Bulk-Heterojunction Solar Cells

Field-effect-tuned lateral organic diodes

Formation Mechanism of Fullerene Cation in Bulk Heterojunction Polymer Solar Cells

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