32 research outputs found
Risk-Managed Lifecycle Costing for Asphalt Road Construction and Maintenance Projects under Performance-Based Contracts
Imaging Charge Transfer State Excitations in Polymer/Fullerene Solar Cells with Time-Resolved Electrostatic Force Microscopy
Imaging Charge Transfer State Excitations in Polymer/Fullerene Solar Cells with Time-Resolved Electrostatic Force Microscopy
We demonstrate nanoscale imaging
of charge transfer state photoexcitations
in polymer/fullerene bulk heterojunction solar cells using time-resolved
electrostatic force microscopy (trEFM). We compare local trEFM charging
rates and external quantum efficiencies (EQE) for both above-gap and
below-gap excitation of the model system poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene]
(MDMO-PPV) and [6,6]-phenyl C<sub>61</sub> butyric acid methyl ester
(PCBM). We show that the local trEFM charging rate correlates with
device EQE for both above-gap and below-gap photoexcitation, demonstrating
that EFM methods have sufficient sensitivity to detect the low EQEs
associated with CT state formation, a result that could be useful
for probing weak subgap excitations in nanostructured materials such
as quantum dot and organometal halide perovskite solar cells. Further,
we use trEFM to map spatial variations in EQE arising from subgap
CT excitation in organic photovoltaics (OPVs) and find that the local
distribution of photocurrent arising from these states is nearly identical
to the spatial variation in EQE from above-gap singlet excitation.
These results are consistent with recent work showing that both above-gap
and below-gap excitation have similar internal quantum efficiency
Effect of Period Length on Forecasting Maintenance and Repair Costs for Heavy Equipment by the Period Cost Based Methodology
Integration of Simulation-Based Cost Model and Multi-Criteria Evaluation Model for Bid Price Decisions
Intermolecular Resonance Correlates Electron Pairs Down a Supermolecular Chain:Antiferromagnetism in K‐Doped p‐Terphenyl
Recent interest in potassium-doped p-terphenyl has been fueled by reports of superconductivity at Tc values surprisingly high for organic compounds. Despite these interesting properties, studies of the structure−function relationships within these materials have been scarce. Here, we isolate a phase-pure crystal of potassium-doped p-terphenyl: [K(222)]2[p-terphenyl3]. Emerging antiferromagnetism in the anisotropic structure is studied in depth by magnetometry and electron spin resonance. Combining these experimental results with density functional theory calculations, we describe the antiferromagnetic coupling in this system that occurs in all 3 crystallographic directions. The strongest coupling was found along the ends of the terphenyls, where the additional electron on neighboring p-terphenyls antiferromagnetically couple. This delocalized bonding interaction is reminiscent of the doubly degenerate resonance structure depiction of polyacetylene. These findings hint toward magnetic fluctuation-induced super- conductivity in potassium-doped p-terphenyl, which has a close analogy with high Tc cuprate superconductors. The new approach described here is very versatile as shown by the preparation of two additional salts through systematic changing of the building blocks