Stable Ultrathin Ag Electrodes by Tailoring the Surface of Plastic Substrates for Flexible Organic Light-Emitting Devices

Abstract

Flexible transparent metal electrodes (FTMEs) have significant application potentials in the fields of flexible optoelectronic devices due to their outstanding optical transmittance and electrical conductivity. However, obtaining excellent optoelectrical properties and mechanical flexibility of FTMEs is challenging because ultrathin metal layers usually follow an island growth mode. In this paper, flexible transparent ultrathin Ag electrodes with high mechanical stability and good optoelectrical properties were exploited by tailoring the surface properties of plastic substrates with ultraviolet−ozone (UVO) treatment for regulating the nucleation and growth kinetics of Ag films. The composite transparent electrodes of Ag (9 nm)/MoO 3 (20 nm) fabricated on the UVO-treated polyethylene terephthalate (PET) substrates possess a low sheet resistance of ∼7.9 Ω/sq, a high optical transmittance of ∼87.2% at 550 nm, a long-period environmental stability of 30 days (∼65 °C, ∼80% humidity), and excellent mechanical flexibility of 100,000 bending cycles at a bending radius of 1.5 mm. These properties are derived from the surface treatment of PET substrates by UVO, which increases substrate surface energy and produces chemical nucleation sites of the phenolic hydroxyl groups. The phenolic hydroxyl groups generated on the PET surface not only provided efficient nucleation sites for subsequent Ag film growth but also formed C−O−Ag bonds between the substrate surface and the Ag layer, which act as "anchor chains" to fix firmly the Ag atoms on the substrate surface. As a universal applicability strategy, the composite electrodes on the UVO-treated polyethylene naphthalate (PEN) and norland optical adhesive 63 (NOA63) substrates also possess excellent optoelectrical properties and mechanical flexibility. Based on the ultrathin Ag composite electrodes, the flexible white organic light-emitting devices with PET, PEN, and NOA63 as substrates present the maximum current efficiencies of 53.0, 77.0, and 65.2 cd/A, respectively.

Physical Aging Behavior of the Side Chain of a Conjugated Polymer PBTTT

“…In recent years, researchers proved the close relationship between the mechanical relaxation process and the side chains of conjugated polymers [ 24 , 25 , 26 ]. In the dynamic mechanical analysis studies of conjugated polymers [ 16 ], the side chain transition temperature has an important influence not only on the side chain motion but also on the mechanical parameters [ 27 ] and other stretchable devices’ properties [ 28 , 29 ]. It was found that a greater drop in modulus change after side-chain relaxation due to the side-chain density increased, and the more mobile structure of side chains induces a drop in several conjugated polymers [ 30 ].…”

Neural-inspired artificial synapses based on low-voltage operated organic electrochemical transistors

“…In stretchable electronics, flexible electrodes can be fabricated on a thin metal coating on a flexible substrate or by adding conductive fillers. 126,127 The most reported stretchable conductors are silver nanowires (AgNWs), 128 Ag epoxy, 129 copper nanowires (CuNWs), 130 CNT, 131 graphene, [132][133][134] and fractal Ag nanostructures 135 included in any elastomer. Conductive polymers and their composites can also serve as flexible electrodes.…”