Bottom Contact Metal Oxide Interface Modification Improving the Efficiency of Organic Light Emitting Diodes

Abstract

The performance of solution-processed organic light emitting diodes (OLEDs) is often limited by non-uniform contacts. In this work, we introduce Ni-containing solution-processed metal oxide (MO) interfacial layers inserted between indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to improve the bottom electrode contact for OLEDs using the poly(p-phenylene vinylene) (PPV) derivative Super-Yellow (SY) as an emission layer. For ITO/Ni-containing MO/PEDOT:PSS bottom electrode structures we show enhanced wetting properties that result in an improved OLED device efficiency. Best performance is achieved using a Cu-Li co-doped spinel nickel cobaltite [(Cu-Li):NiCo2O4], for which the current efficiency and luminous efficacy of SY OLEDs increased, respectively, by 12% and 11% from the values obtained for standard devices without a Ni-containing MO interface modification between ITO and PEDOT:PSS. The enhanced performance was attributed to the improved morphology of PEDOT:PSS, which consequently increased the hole injection capability of the optimized ITO/(Cu-Li):NiCo2O4/PEDOT:PSS electrode.

Pseudo-bilayered inverted organic solar cells using the Marangoni effect

“…[39][40][41]43,44,55 The structural constraint can result in stability issues partly because of the hygroscopicity [56][57][58] and acidity [59][60][61] of PEDOT:PSS, which is the most widely used substance for transporting holes from active layers. 62,63 In fact, the air stability (RH > 40%) of PEDOT-based OSCs with a normal structure was demonstrated to be low compared with that of ZnO-based OSCs with an inverted structure. 64 In fact, 2PACzbased OSCs with a normal structure had low air stability despite their higher light stability compared with PEDOT-based OSCs (Fig.…”

Unraveling Degradation Processes and Strategies for Enhancing Reliability in Organic Light-Emitting Diodes

“…The light output was reduced by an order of magnitude when comparing devices kept under nitrogen to those kept in ambient conditions. Water is also known to cause fluorescence quenching [224]. The two components, oxygen and water, are known to react differently with various materials.…”

“…OLEDs are affected by oxygen and water as illustrated in Figure 12. Several substances, such as electropositive metal cathode oxidation releasing elemental hydrogen, disintegrating chelate molecules causing a variety of reactions in the end products, photo-or electrochemical processes oxidizing organic molecules, creating filled traps and/or free charge carriers from charge-transfer doping, and altering the structure of materials, including crystallization, can initiate a variety of processes that cause the damage [120,[224][225][226][227][228][229].…”

Circular economy of ITO thin films deposited on glass obtained from degraded OLED devices

“…TCO is a type of semiconductor that offers: high optical transparency (≈ 90%) to light crossing, good electrical conductivity (from ≈7.10 -5 to 5.10 -4 Ω.cm), sheet resistance (from 5 to 15 Ω/ ) and workfunction between 4.5 to 5.3 eV. This material is used as an electrode anode, promoting the injection of hole charge carriers inside the OLED 16 .…”