Abstract
Quantum dot light-emitting devices have emerged as an important technology for display applications. Their emission is a result of recombination between positive and negative charge carriers that are transported through the hole and electron conductive layers, respectively. The selection of electron or hole transport materials in these devices not only demands the alignment of energy levels between the layers but also balances the flow of electrons and holes toward the recombination sites. In this work, we examine a method for device optimization through control of the charge carrier kinetics. We employ impedance spectroscopy to examine the mobility of charge carriers through each of the layers. The derived mobility values provide a path to estimate the transition time of each charge carrier toward the emitting layer. We suggest that an optimal device structure can be obtained when the transition times of both charge carriers toward the active layer are similar. Finally, we examine our hypothesis by focusing on thickness optimization of the electron transport layer.
Highlights
Semiconducting quantum dots (QDs) carry tunable optical properties and good stability and can be synthesized following scalable colloidal synthesis routes
QD characterization The emission properties of quantum dot light-emitting devices (QLEDs) are controlled by the optical properties of the nanoparticles
We showed how impedance spectroscopy analysis can be employed for the measurement of the charge transport time through hole or electron transport layers
Summary
Semiconducting quantum dots (QDs) carry tunable optical properties and good stability and can be synthesized following scalable colloidal synthesis routes. In a typical QLED, the nanoparticles emit light as a result of radiative recombination between positive and negative charge carriers. The efficiency of charge transport between layers depends on the alignment of energy levels within a device.
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