Effects of the interfacial charge injection properties of silver nanowire transparent conductive electrodes on the performance of organic light-emitting diodes
We investigated the charge injection properties of silver nanowire networks (AgNWs) in a composite-like structure with poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) (PEDOT:PSS). The composite films acted as the anodes and hole transport layers (HTLs) in organic light-emitting diodes (OLE...
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Veröffentlicht in: | Journal of applied physics 2017-03, Vol.121 (10) |
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Sprache: | eng |
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Zusammenfassung: | We investigated the charge
injection properties of silver nanowire networks (AgNWs) in a
composite-like structure with poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate)
(PEDOT:PSS). The composite films acted as the anodes and hole transport layers (HTLs) in organic light-emitting diodes
(OLEDs). The
current density (J)–voltage (V)–luminance
(L) characteristics and power efficiency (ε) of the
OLEDs were
measured to determine their electrical and optical properties. The charge injection properties of
the AgNWs in the OLEDs during operation were characterized via impedance spectroscopy
(IS) by determining the variations in the capacitances (C) of the devices
with respect to the applied V and the corresponding frequency
(f). All measured results were compared with results for OLEDs fabricated on indium tin
oxide (ITO) anodes. The OLEDs on AgNWs showed lower L and ε
values than the OLEDs on ITO. It was also observed that AgNWs exhibit excellent
charge injection
properties and that the interfaces between the AgNWs and the HTL have very small
charge injection
barriers, resulting in an absence of charge carrier traps when charges move across
these interfaces. However, in the AgNW-based OLED, there was a large mismatch in the number of injected
holes and electrons. Furthermore, the highly conductive electrical paths of the
AgNWs in the composite-like AgNW and PEDOT:PSS structure allowed a large leakage current
of holes that did not participate in radiative recombination with the electrons; consequently,
a lower ε was observed for the AgNW-based OLEDs than for the ITO-based
OLEDs. To match
the injection of electrons by the electron transport layer (ETL) in the AgNW-based
OLED with that
of holes by the AgNW/PEDOT:PSS composite anode, the electron injection barrier of the ETL was decreased by
using the low work function polyethylenimine ethoxylated (PEIE) doped with n-type cesium
carbonate (Cs2CO3). With the doped-PEIE, the performance of
the AgNW-based OLED was significantly enhanced through the balanced injection of holes
and electrons, which clearly verified our analysis results by IS. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.4978368 |