期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 112, 期 14, 页码 4227-4232出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1421042112
关键词
glasses; organic semiconductors; molecular orientation; physical vapor deposition; high-throughput characterization
资金
- US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-SC0002161]
- National Science Foundation [DMR-1234320]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1234320] Funding Source: National Science Foundation
Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. We apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T-substrate) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by Tsubstrate/T-g, where T-g is the glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form stable glasses with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. By showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.
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