Study On Charge Balance Injection And Transport Of Quantum Dots Electroluminescent Diodes

After decades of relentless efforts by numerous researchers,there exist numerous types of quantum dot materials nowadays,and the main ones that have received more attention so far are traditional colloidal quantum dots,calcium titanite quantum dots and carbon quantum dots.Quantum dot electroluminescent diodes(QLED)have also attracted great attention due to their unique optical and physicochemical properties.Quantum dot-based displays are expected to be the next-generation display technology that surpasses organic light-emitting diodes(OLED).However,one of the main factors affecting the efficiency of QLED devices is the balanced carrier injection and transport,and this has been the main research direction to improve the performance of QLED devices.In this paper,we design and optimize the device structure to improve the device performance with this research direction.Details are as follows.1.The main reasons for the poor performance of carbon dot-based electroluminescent devices(CDs-LEDs)are the aggregation quenching of carbon dots(CDs)and the poor morphology of solid-state thin films.To address this issue,this study used the approach of host-guest doping,with TPBi as the host and CDs as the guest,and both were doped as the layer that emits light.The good dispersion of CDs in TPBi improves the film morphology of the luminescent layer,and the hole transport of CDs is higher than the electron transport,so that TPBi with electron transport properties can also play a role in charge balancing as the main material.Introducing an organic hole transport layer into the device structure can improve the inj ection of holes into the emissive layer,while suppressing the direct injection of electrons to the opposite electrode through the emissive layer,thereby confining more excitons within the emissive layer,this improves the charge balance and recombination efficiency within the emissive layer.With its excellent hole transport properties,PTAA maximizes the hole injection and transport,thus improving the charge balance and regulating the carrier complex region,suppressing the complex at the outer surface of the light-emitting layer,and preparing a high-performance pure orange-yellow CDs-LED with a peak luminance at 574 nm,a maximum luminance of 9754 cd/m~2,and an external quantum efficiency(EQE)of 2.82%.2.High-performance semi-transparent QLED devices were prepared by controlling the balance of charge injection and transport.Al was used as the electrode modification layer to modify the contact interface between the translucent metal electrode Ag and the electron transport layer ZnO.2 nm of Al was used as the interface modification layer to improve the injection and transport of electrons.In addition,the Al/Ag metal film is used as the transparent top electrode of the translucent QLED,and its transmittance is higher than that of the Ag electrode.The addition of a thin film of aluminum not only enhances the electrical characteristics of the device but also raises the average visible light transmittance of the translucent QLED device.Different metaldoped ZnO was adjusted to function as an electron transport layer and enhance the charge balance in the device,resulting in high-performance transparent QLED devices.The final translucent QLED with an average visible transmittance of 58.64%,maximum brightness and current efficiency of 387506 cd/m~2 and 52.4 cd/A on the bottom side,and maximum brightness and current efficiency of 63751 cd/m~2 and 6.2 cd/A on the top side,respectively,with a total EQE of 13.49%was obtained.