Impedance Spectroscopy: A Versatile Technique to Understand Solution‐Processed Optoelectronic Devices

Abstract

Solution‐processed optoelectronic devices based on conjugated polymers, colloidal quantum dots (CQDs), halide perovskites, and so on are now emerging as a new‐generation semiconductor technology which prevails its conventional counterparts in terms of low fabrication cost, ease of scalable manufacturing, and abundant material designability. However, the solution‐processed thin films obtained through spin‐coating, spray, inkjet printing, and doctor blading usually suffer from low film quality and a high defect density especially at the interfaces of different functional layers. Currently, the most significant subject is to address the non‐ideal interfaces for achieving improved performance of the devices. Impedance spectroscopy (IS) is a universal technique that can help to examine the charge behavior at the interfaces in an electrochemical or solid‐state multilayered device. Owing to its ability to elucidate the charge transfer, charge transport, and accumulation within the interfaces of electrochemical or multilayered devices with minimal effects to the devices themselves, the use of IS has increased vividly in the last decades. This review provides the basic principles of IS and its applications on solution‐processed optoelectronic devices.

Illustrating the Shell Thickness Dependence in Alloyed Core/Shell Quantum-Dot-Based Light-Emitting Diodes by Impedance Spectroscopy

“…The average capacitances over the applied voltage were estimated to be 8, 7.5, and 5 nF, respectively, for the LEDs constructed with QD 1 , QD 2 , and QD 3 . No obvious change in the capacitances was recorded for all kinds of devices under applied bias, which is consistent with our previous observation on the capacitance of the full QD-LED device . The R s plays a significant role in the LEDs performance.…”

“…No obvious change in the capacitances was recorded for all kinds of devices under applied bias, which is consistent with our previous observation on the capacitance of the full QD-LED device. 29 The R s plays a significant role in the LEDs performance. The R s of devices are depicted in Figure 4d.…”

“…Impedance spectroscopy (IS) is a powerful tool to illustrate the charge accumulation, injection, and transportation across the interface of the charge transporting and emissive layers in the solution-processed optoelectronic devices. 29 In this study, IS has been adopted as a competent and universal character- ization technique in the investigation of alloyed core/shell Cd x Zn 1−x Se y S 1−y /ZnS (CdSe/ZnS) QDs-based electroluminescent devices. For the comprehensive investigation of effects of shell thickness on the performance of the QD-LED, electron-only symmetric and full device architectures were explored for the QDs with varied shell thickness.…”

“…Impedance spectroscopy (IS) is a powerful tool to illustrate the charge accumulation, injection, and transportation across the interface of the charge transporting and emissive layers in the solution-processed optoelectronic devices . In this study, IS has been adopted as a competent and universal characterization technique in the investigation of alloyed core/shell Cd x Zn 1– x Se y S 1– y /ZnS (CdSe/ZnS) QDs-based electroluminescent devices.…”

Effectiveness of Solvent Vapor Annealing on Optoelectronic Properties for Quasi-2D Organic–Inorganic Hybrid Perovskite Light-Emitting Diodes

“…Because the numerical values of CPE-P are close to 1 for both PeLEDs, the CPE behaves as the capacitors, and the values of the capacitance such as CPE-T are in Table . The combination of R rec and CPE generates the semicircle for the spectra. ,− Apparently, the one that was processed with DMF produced a smaller semicircle than the reference film, leading to the decrease in R rec . Figure b gives the electroluminescence (EL) spectra for both PeLEDs when a bias voltage of 3 V was applied.…”