eCommons

 

Fluctuations Near Thin Films Of Polymers, Organic Photovoltaics, And Organic Semiconductors Probed By Electric Force Microscopy

Other Titles

Abstract

Scanned probe microscopy has the ability to image a surface by probing dynamic fluctuations. In this work, we measure surface-induced fluctuations as noise in the cantilever resonance frequency. We provide a theoretical basis of surface-induced cantilever frequency noise, which we then use to study thin polymer films, organic photovoltaics, and organic semiconductors. Over polymer films we demonstrate that the observed frequency noise is due to fluctuations in the sample's electric polarization. We have developed a theory that links these fluctuations to the dielectric function of the polymer. Our theory correctly predicts the magnitude and spectral shape of the observed frequency noise, as well as its dependence on distance and tip-voltage. Over polymer-blend heterojunction solar cells we find that in the presence of light, cantilever frequency noise increases by almost two orders of magnitude and, remarkably, shows a wavelength dependence that follows the absorption spectrum of one of the polymer components. We attribute the light-induced noise to charge trapping and detrapping. In molecular organic semiconductors, we investigate charge-induced frequency noise. Charge motion in these materials has to date been described using microscopic chargehopping models, which essentially neglect long-range inter-carrier interactions. Here we demonstrate that inter-carrier interactions cannot be ignored in a frequency noise experi- ment because these interactions suppress fluctuations in the electrostatic potential by several orders of magnitude. keywords: transistor, poly(3-hexylthiophene) (P3HT), N,N'-Diphenyl-N,N'-di(3-tolyl)-4benzidine (TPD),

Journal / Series

Volume & Issue

Description

Sponsorship

Date Issued

2013-01-28

Publisher

Keywords

transistor; poly(3-hexylthiophene) P3HT; poly(3-hexylthiophene) (P3HT); TPD

Location

Effective Date

Expiration Date

Sector

Employer

Union

Union Local

NAICS

Number of Workers

Committee Chair

Ralph, Daniel C

Committee Co-Chair

Committee Member

Mueller, Erich
Parpia, Jeevak M
Marohn, John A.

Degree Discipline

Physics

Degree Name

Ph. D., Physics

Degree Level

Doctor of Philosophy

Related Version

Related DOI

Related To

Related Part

Based on Related Item

Has Other Format(s)

Part of Related Item

Related To

Related Publication(s)

Link(s) to Related Publication(s)

References

Link(s) to Reference(s)

Previously Published As

Government Document

ISBN

ISMN

ISSN

Other Identifiers

Rights

Rights URI

Types

dissertation or thesis

Accessibility Feature

Accessibility Hazard

Accessibility Summary

Link(s) to Catalog Record