A thin layer of NaCl with a thickness of "~ 3 nm" was deposited on 15 nm ZnO NP+PEIE/ 80 nm SY in an OLED stack. A super thin layer of NaCl acts as a surface modifier increasing the electron injection, current density, external quantum efficiency and finally the overall performance of the OLED. The optical, electrical and morphological properties of OLEDs are enhanced by both solution-processed and vacuum-processed NaCl deposition. Significant enhancement in the EQE and illuminance of the NaCl-based device were exhibited compared with standard devices and are allowed to use because of their abundant availability and nontoxicity for efficient OLEDs.
The functional layer encompasses ~15 nm thick Zinc Oxide nanoparticles (ZnO NPs) in a polyethylenimine ethoxylated (PEIE) matrix. PEIE acts as a surface modifier on ZnO NPs and also interlinks the individual ZnO NPs resulting in enhanced electron injection and transport. Owing to the deep valence band energy state of the ZnO NPs, the hole mobility is reduced significantly. The optimized light outcoupling in the OLED using the functional layer is achieved with the combination of optical light outcoupling simulation and thickness optimization by spin coating. The outcome of these optimizations is a solution processable high efficient, low-cost OLED.
Nanometer-thick, ultrathin coatings applied over a large area are of paramount importance for various application fields such as biomedicine, space and automotive, organic electronics, memory devices, or energy storage devices. So far wet chemical deposition as a cost-effective, scalable, and versatile method can only be used for thicker deposits, at least 30nm in thickness.
In this work, the formation of uniform ultra-thin coatings with thicknesses below 15nm using a nature-inspired, roll-to-roll compatible Spray-on-Screen (SoS) technology is reported. For this, the finite micro-droplet generation of Ultrasonic Spray Coating (USSC) is combined with the coating formation from a screen printing mesh. Hydrophobic micro-threads of the mesh, resembling the micro-hair on the legs of water striders, produce millidroplets from micro droplets, and when applying an external pressure to the mesh, dynamic wetting is enforced. OLEDs are build using this Spray-on-Screen technology.
OLEDs consisting of Au-NPs sandwiched between anode and hole injection layer, and close to an active layer inside PEDOT:PSS is fabricated by Ultrasonic Spray Coating (USSC). Optimized surface coverage of Au-NPs on ITO facilitates efficient charge injection and an optimized position of the Au-NPs away from the active layer accelerates the radiative recombination. Obtained results indicate that USSC could effortlessly tune the surface coverage and the vertical position of the Au-NPs to enhance the OLED’s efficacy. This paves the way for the fabrication of large area, high efficient OLEDs with USSC.
Lighting today is expected to be light weighted, flexible, highly efficient, non-expensive and fabricated in an environment friendly way. Organic light emitting diodes (OLEDs) meet all of these requirements and can be applied using inexpensive and roll-to-roll compatible printing techniques. This work demonstrates the ultrasonic spray coating (USSC) of polyethylenimine (PEI) and polyethylenimine(ethoxylated) (PEIE) as electron injection/transport layer (EIL/ETL) for OLEDs. This high-end printing technique employs ultrasonic atomization to break down a liquid into a spray of homogeneous small (20 µm) droplets. The PEI(E) layer was optimised using USSC and subjected to a complete morphological and electro-optical characterisation. For all manufactured devices current and voltage characteristics and luminous performances were obtained. This study confirms the versatility of USSC and the suitability of PEI(E) as excellent EIL/ETL for OLEDs and paves the way towards fully printed devices.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.