Correlating the scattered intensities of P3HT and PCBM to the current densities of polymer solar cells

Gomez, Enrique D.; Barteau, Katherine P.; Wang, He; Toney, Michael F.; Loo, Yueh Lin

doi:10.1039/c0cc02927k

Cited by 104 publications

(108 citation statements)

References 21 publications

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“…Moreover, we observe a high Herman's orientation factor S ≈ 0.82, indicating a strong preference for face-on stacking of the polymer backbone with respect to the substrate, which according to literature benefits vertical CT across the active layer. 11b, 18 To obtain a measure for the majority charge-carrier mobility of the blend, devices were probed with photo-charge extraction by linearly increasing voltage, which yielded values of (1−2) × 10 −4 cm 2 /(V·s) (SI). Despite the strong effect of DIO on the blend nanostructure, for 2:3 PTNT:PC 71 BM layers with similar thickness, the external quantum efficiency (EQE) increased from only ∼50% to ∼60% in the 350−550 nm absorption region and resulted in a small increase in J sc by ∼1.5 mA cm −2 .…”

Section: * S Supporting Informationmentioning

confidence: 99%

A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics

Kroon

Mendaza²,

Himmelberger

et al. 2014

J. Am. Chem. Soc.

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A new tetracyclic lactam building block for polymer semiconductors is reported that was designed to combine the many favorable properties that larger fused and/or amide-containing building blocks can induce, including improved solid-state packing, high charge carrier mobility, and improved charge separation. Copolymerization with thiophene resulted in a semicrystalline conjugated polymer, PTNT, with a broad bandgap of 2.2 eV. Grazing incidence wide-angle X-ray scattering of PTNT thin films revealed a strong tendency for face-on πstacking of the polymer backbone, which was retained in PTNT:fullerene blends. Corresponding solar cells featured a high open-circuit voltage of 0.9 V, a fill factor around 0.6, and a power conversion efficiency as high as 5% for >200 nm thick active layers, regardless of variations in blend stoichiometry and nanostructure. Moreover, efficiencies of >4% could be retained when thick active layers of ∼400 nm were employed. Overall, these values are the highest reported for a conjugated polymer with such a broad bandgap and are unprecedented in materials for tandem and particularly ternary blend photovoltaics. Hence, the newly developed tetracyclic lactam unit has significant potential as a conjugated building block in future organic electronic materials.

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Section: * S Supporting Informationmentioning

confidence: 99%

A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics

Kroon

Mendaza²,

Himmelberger

et al. 2014

J. Am. Chem. Soc.

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“…The crystalline PCBM shows a pattern of distinct diffraction spots (instead of rings), indicating crystallites having a preferential orientation with respect to the substrate surface. [ 36 ] Previous X-ray diffraction measurements [ 44 ] of single crystals show that PCBM crystallizes in a monoclinic unit cell (P2 1 /n) with four molecules per unit cell. We may expect the PCBM molecules to pack in thin fi lms in a fashion similar to single crystals, as has been previously observed for instance in similar studies of thin pentacene fi lms.…”

Section: Pcbm Crystallization Upon Thermal Annealingmentioning

confidence: 99%

“…However, in practice this approach necessitates complex modelling [ 35 ] and measurements of a standard sample with a known crystallinity. [ 36 ] In addition, we discuss the infl uence of the interfacial dipoles and crystallinity on device parameters processed under the same conditions.…”

mentioning

confidence: 99%

Quantifying Interfacial Electric Fields and Local Crystallinity in Polymer–Fullerene Bulk‐Heterojunction Solar Cells

Gearba

Mills

Morris

et al. 2011

Adv Funct Materials

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The challenges of experimentally probing the physical and electronic structures of the highly intermixed organic semiconductor blends that comprise active layers in high‐performance organic photovoltaic (OPV) cells ultimately limit the fundamental understanding of the device performance. We use Fourier‐transform IR (FTIR)‐absorption spectroscopy to quantitatively determine the interfacial electric field in blended poly(3‐hexylthiophene) (P3HT):phenyl‐ C61‐butyric acid methyl ester (PCBM) thin films. The interfacial electric field is ≈0.2 V nm−1 in the as‐spun film and blends annealing at temperatures as high as 150 °C, which is the optimal annealing temperature in terms of OPV performance. The field decreases to a negligible value upon further annealing to 170 °C, at which temperature PCBM changes from amorphous to crystalline and the open‐circuit voltage of the solar cell decreases from 0.62 to 0.4 V. In addition, our measurements also allow determination of the absolute degree of crystallinity within the acceptor material. The roles of interfacial field and local crystallinity in OPV device performance are discussed.

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“…This means that the crystallites with o less than the Bragg angle cannot be detected by 2D GIXD. A local specular experiment can complement GIXD by providing intensities for the crystallites with o less than the Bragg angle [44][45][46] . However, the signal-to-noise ratio was found unsatisfactory in such an experiment for the (010) reflection.…”

Section: Articlementioning

confidence: 99%

Molecular origin of high field-effect mobility in an indacenodithiophene–benzothiadiazole copolymer

et al. 2013

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One of the most inspiring and puzzling developments in the organic electronics community in the last few years has been the emergence of solution-processable semiconducting polymers that lack significant long-range order but outperform the best, high-mobility, ordered semiconducting polymers to date. Here we provide new insights into the charge-transport mechanism in semiconducting polymers and offer new molecular design guidelines by examining a state-of-the-art indacenodithiophene-benzothiadiazole copolymer having field-effect mobility of up to 3.6 cm 2 V À 1 s À 1 with a combination of diffraction and polarizing spectroscopic techniques. Our results reveal that its conjugated planes exhibit a common, comprehensive orientation in both the non-crystalline regions and the ordered crystallites, which is likely to originate from its superior backbone rigidity. We argue that charge transport in high-mobility semiconducting polymers is quasi one-dimensional, that is, predominantly occurring along the backbone, and requires only occasional intermolecular hopping through short p-stacking bridges.

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Correlating the scattered intensities of P3HT and PCBM to the current densities of polymer solar cells

Cited by 104 publications

References 21 publications

A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics

A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics

Quantifying Interfacial Electric Fields and Local Crystallinity in Polymer–Fullerene Bulk‐Heterojunction Solar Cells

Molecular origin of high field-effect mobility in an indacenodithiophene–benzothiadiazole copolymer

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