Influence of Vapor Deposition on Structural and Charge Transport Properties of Ethylbenzene Films
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- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States, The Institute for Molecular Engineering, Argonne National Laboratory, Lemont, Illinois 06349, United States
- Advanced Leadership Computing Facility, Argonne National Laboratory, Lemont, Illinois 06349, United States
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
Organic glass films formed by physical vapor deposition exhibit enhanced stability relative to those formed by conventional liquid cooling and aging techniques. Recently, experimental and computational evidence has emerged indicating that the average molecular orientation can be tuned by controlling the substrate temperature at which these "stable glasses" are grown. In this work, we present a comprehensive all-atom simulation study of ethylbenzene, a canonical stable-glass former, using a computational film formation procedure that closely mimics the vapor deposition process. Atomistic studies of experimentally formed vapor deposited glasses have not been performed before, and this study therefore begins by verifying that the model and method utilized here reproduces key structural features observed experimentally. Having established agreement between several simulated and experimental macroscopic observables, simulations are used to examine the substrate temperature dependence of molecular orientation. The results indicate that ethylbenzene glasses are anisotropic, depending upon substrate temperature, and that this dependence can be understood from the orientation present at the surface of the equilibrium liquid. By treating ethylbenzene as a simple model for molecular semiconducting materials, a quantum-chemical analysis is then used to show that the vapor-deposited glasses exhibit decreased energetic disorder and increased magnitude of the mean-squared transfer integral relative to isotropic, liquid-cooled films, an effect that is attributed to the anisotropic ordering of the molecular film. These results suggest a novel structure function simulation strategy capable of tuning the electronic properties of organic semiconducting glasses prior to experimental deposition, which could have considerable potential for organic electronic materials design.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1351665
- Alternate ID(s):
- OSTI ID: 1369460; OSTI ID: 1393175
- Journal Information:
- ACS Central Science, Journal Name: ACS Central Science Vol. 3 Journal Issue: 5; ISSN 2374-7943
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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