Application of MIS-CELIV technique to measure hole mobility of hole-transport material for organic light-emitting diodes

Chiho Katagiri,Cigdem Yumusak,Ken-Ichi Nakayama,Niyazi Serdar Sariciftci,Tsukasa Yoshida,Matthew Schuette White

doi:10.1063/1.5045711

Abstract

Injection-charge extraction by linearly increasing voltage in metal-insulator-semiconductor structures (MIS-CELIV) is applied for the hole mobility measurement of N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)-benzidine (NPB), which is a standard hole-transporting material for organic light-emitting diodes. Ideal transient currents in agreement with the theory are observed in the NPB film due to its amorphous and homogenous structure, which is regarded as a continuous dielectric. This ideal response enables us to discuss the validity of the MIS-CELIV mobility by comparing its absolute value with that of the conventional space-charge-limited current method. In addition, to establish an experimental guideline for precise measurements, the effect of the voltage drop on the insulator is investigated.

Highlights

Charge-carrier mobility is one of the key parameters for organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs)
The TOF method has been conventionally used for measuring the charge-carrier mobility in organic semiconductors; the electron and hole mobilities are directly estimated from the transport time of the photogenerated charge carriers
The mobility is estimated from the current transients by the extraction of the equilibrium or photogenerated charge carriers, for the dark charge extraction by linearly increasing voltage (CELIV) and photo-CELIV measurements, respectively

Summary

Introduction

Charge-carrier mobility is one of the key parameters for organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Chiho Katagiri,[1,2] Tsukasa Yoshida,[1] Matthew Schuette White,[3] Cigdem Yumusak,[4] Niyazi Serdar Sariciftci,[4] and Ken-ichi Nakayama1,2,a 1Department of Organic Materials Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan 2Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan 3Department of Physics, University of Vermont, Burlington, Vermont 05405, USA 4Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria (Received 23 June 2018; accepted 20 September 2018; published online 1 October 2018)

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