Gagorik, Adam
(2014)
Charge Transport in Disordered Materials.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
This thesis is focused on on using Monte Carlo simulation to extract device relevant properties, such as the current voltage behavior of transistors and the efficiency of photovoltaics, from the hopping transport of molecules.
Specifically, simulation is used to study organic field-effect transistors (OFETs) and organic photovoltaics (OPVs).
For OFETs, the current was found to decrease with increasing concentration of traps and barriers in the system.
As the barrier/trap concentration approaches 100%, the current recovers as carrier begin to travel through the manifold of connected trap states.
Coulomb interactions between like charges are found to play a role in removing carriers from trap states.
The equilibrium current in OFETs was found to be independent of charge injection method, however, the finite size of devices leads to an oscillatory current.
Fourier transforms of the electrical current show peaks that vary non-linearly with device length, while being independent of device width.
This has implications for the mobility of carriers in finite sized devices.
Lastly, the presence of defects and high barriers (> 0.4 eV) was found to produce negative differential resistance in the saturation region of OFET curves, unlike traps.
While defects and barriers prohibit carriers from reaching the drain at high voltages, the repulsive interaction between like charged carriers pushes charges around the defects.
For OPVs, the effects of device morphology and charge delocalization were studied.
Fill factors increased with domain size in monolayer isotropic morphologies, but decreased for band morphologies.
In single-phase systems without Coulomb interactions, astonishingly high fill factors (70%) were found.
In multilayer OPVs,a complex interplay of domain size, connectivity, tortuosity, interface trapping, and delocalization determined efficiency.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
30 January 2014 |
| Date Type: |
Publication |
| Defense Date: |
3 December 2013 |
| Approval Date: |
30 January 2014 |
| Submission Date: |
5 December 2013 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
213 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Monte Carlo, Organic Semiconductors, Disordered Transport, Organic Photovoltaics, Electronics, Organic Field Effect Transistors |
| Date Deposited: |
30 Jan 2014 20:17 |
| Last Modified: |
15 Nov 2016 14:16 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/20205 |
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