Charge transport in Spiro-OMeTAD investigated through space-charge-limited current measurements

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Title: Charge transport in Spiro-OMeTAD investigated through space-charge-limited current measurements
Author(s): Rohr, J
Shi, X
Haque, S
Kirchartz, T
Nelson, J
Item Type: Journal Article
Abstract: Extracting charge-carrier mobilities for organic semiconductors from space-charge-limited conduction measurements is complicated in practice by nonideal factors such as trapping in defects and injection barriers. Here, we show that by allowing the bandlike charge-carrier mobility, trap characteristics, injection barrier heights, and the shunt resistance to vary in a multiple-trapping drift-diffusion model, a numerical fit can be obtained to the entire current density–voltage curve from experimental space-charge-limited current measurements on both symmetric and asymmetric 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) single-carrier devices. This approach yields a bandlike mobility that is more than an order of magnitude higher than the effective mobility obtained using analytical approximations, such as the Mott-Gurney law and the moving-electrode equation. It is also shown that where these analytical approximations require a temperature-dependent effective mobility to achieve fits, the numerical model can yield a temperature-, electric-field-, and charge-carrier-density-independent mobility. Finally, we present an analytical model describing trap-limited current flow through a semiconductor in a symmetric single-carrier device. We compare the obtained charge-carrier mobility and trap characteristics from this analytical model to the results from the numerical model, showing excellent agreement. This work shows the importance of accounting for traps and injection barriers explicitly when analyzing current density–voltage curves from space-charge-limited current measurements.
Publication Date: 12-Apr-2018
Date of Acceptance: 23-Jan-2018
URI: http://hdl.handle.net/10044/1/56701
DOI: https://dx.doi.org/10.1103/PhysRevApplied.9.044017
ISSN: 2331-7019
Publisher: American Physical Society
Journal / Book Title: Physical Review Applied
Volume: 9
Issue: 4
Copyright Statement: © 2018 American Physical Society
Keywords: Science & Technology
Physical Sciences
Physics, Applied
Physics
DOUBLE-JUNCTION DIODES
POLYMER SOLAR-CELLS
ORGANIC SEMICONDUCTORS
CONJUGATED POLYMERS
WORK FUNCTION
DIFFUSION
MOBILITY
VOLTAGE
SOLIDS
TRAPS
Publication Status: Published
Article Number: 044017
Appears in Collections:Physics
Experimental Solid State
Centre for Environmental Policy
Faculty of Natural Sciences



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