Impedance measurements on QLED devices: analysis of high-frequency loop in terms of material properties
- PDF / 970,554 Bytes
- 8 Pages / 595.224 x 790.955 pts Page_size
- 28 Downloads / 239 Views
ORIGINAL PAPER
Impedance measurements on QLED devices: analysis of high-frequency loop in terms of material properties Chen You1 · Alex Titov2 · Baek Hyun Kim2 · Mark E. Orazem1 Received: 30 May 2020 / Revised: 10 July 2020 / Accepted: 13 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Electrochemical impedance spectroscopy is used to study red and green quantum-dot light-emitting diodes devices. The high-frequency loop is interpreted in terms of the thickness, dielectric constant, and resistivity distribution of the holeinjection layer. The analysis employed the device capacitance obtained from a measurement model analysis, the film thickness measured by scanning electron microscopy, and an interpretation of the impedance based on a power-law model. Impedance measurements performed on hole-transport–only devices yielded results that were consistent with the interpretation of the high-frequency capacitive loop in terms of the properties of the hole-injection layer. Keywords Quantum-dot light-emitting diodes · Electrochemical impedance spectroscopy · Power-law model · Regression analysis
Introduction Electrochemical impedance spectroscopy (EIS) has been applied over the decades to study the light-emitting diode (LED) devices and could provide an ability to characterize the electrical properties of the material and the interfaces inside the device. Cho et al. [1] studied the effects of plasma treatment on the surface of indium-tin oxide (ITO) anodes on the OLEDs using different gases. Different values of the contact resistance, the parallel resistance, and the parallel capacitance inferred by the EIS analysis were attributed to the removal of contaminants and to changes in the work function of ITO. Nowy et al. [2] used EIS to investigate the charge-carrier injection properties with different anodes and anode treatments in bottom-emitting OLEDs. Capacitance, This paper is submitted in celebration of the 65th birthday of Prof. Fritz Scholz. One of the authors, Mark Orazem, met Prof. Scholz at the “First Workshop of Material Science for Corrosion Protection” held in 2017 in Santiago, Chile, where we discussed the importance of education in electrochemistry. Mark E. Orazem
[email protected] 1
Department of Chemical Engineering, University of Florida, Gainesville, FL, 32611, USA
2
NanoPhotonica Inc. Research Lab, UF Innovate | The Hub, Gainesville, FL 32601 USA
trapped and interfacial charges, and the dynamics of injected charges were analyzed to study degradation processes. Hsiao et al. [3] used EIS to study the interfacial capacitance of polymer light-emitting diode devices, and an additional capacitive loop was associated with the bulk of the PEDOT layer. Kwak et al. [4] proposed a method to examine the thermal degradation of OLEDs by EIS and infrared imaging. The OLED with poor electrical properties showed a fairly high temperature during the operation and a short lifetime. Cai et al. [5] and Chulkin et al. [6, 7] measured impedance spectroscopy on OLED devices to study the char
Data Loading...
