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Ultrathin metal films emerge as an innovative category of transparent electrodes in recent decades, holding great promises enabling the next-generation flexible organic light-emitting devices (OLEDs). Although metal thin films with polymer nucleation inducers have been extensively studied in OLEDs, satisfying the requirements of both superior optoelectrical and high optical outcoupling characteristics is still challenging. Here, we demonstrate a metal oxide/ultrathin Ag/polymer (MAP) composite electrode with low sheet resistance of 15.1 Ω/sq, high transmittance of 87.4% at 550 nm, and smooth morphology with surface roughness of 0.768 nm. Besides, the composite electrodes significantly enhance the outcoupling of the light trapped in OLEDs due to the relatively high-refractive index polymer. Flexible OLEDs with the MAP anodes exhibit over 2.3 times enhancement in efficiency to that of indium tin oxide (ITO)-based OLEDs. The flexible OLEDs can survive 1000 bending cycles at a bending radius of 8 mm with negligible decrease in electroluminescent performance. [ABSTRACT FROM AUTHOR]

We report an ultrathin Au transparent electrode with the thickness of only 4.4 nm based on an S-1805/Ag hybrid nucleation layer and its application in flexible organic light-emitting devices (OLEDs) as the replacement of indium tin oxide (ITO) anode. The Volmer–Weber growth mode of the deposited Au film has been suppressed successfully by using the hybrid nucleation layer, in which the S-1805 acts as a substrate modification layer and 0.6 nm Ag acts as a seeding layer. The resulting ultrathin Au film with the thickness of 4.4 nm shows high transparency, high conductivity, and ultrasmooth surface. A 25% improvement in efficiency has been demonstrated for the OLEDs with ultrathin Au anodes compared to the ITO-based devices. The application of the high-performance ultrathin Au electrodes in OLEDs results in high flexibility and mechanical robustness with small performance variations after 2100 bending cycles with a 7.5 mm bending radius. [ABSTRACT FROM AUTHOR]

Fe3O4 has been demonstrated to be an efficient p-dopant in improving the performance of organic light-emitting devices. This paper investigates in detail the role of Fe3O4 in improving the hole injection and the hole transport by the ultraviolet/visible/near-infrared absorption, x-ray, and ultraviolet photoelectron spectroscopy. The results demonstrated that Fe3O4 as a p-dopant has different effectiveness when it is doped into different host materials. The improved properties of the OLEDs with the p-doped N, N'-diphenyl-N,N'-bis (1,1'-biphenyl)-4,4'-diamine layer is mainly due to the enhanced hole injection through the lowering of the hole injection barrier, while the enhanced hole transport plays a more important role for the OLEDs with the p-doped 4,4',4”-tris (3-methylphenylphenylamino) triphenylamine due to their higher ability in the formation of charge transfer complex. [ABSTRACT FROM PUBLISHER]

Transparent conductive electrodes, as transmission windows of photons and electrons, play important roles in high‐performance organic optoelectronic devices. The replacement of widely used indium tin oxide (ITO) electrodes has been attempted due to the increasing cost and intrinsically brittle characteristics of ITO. Ultrathin metal films, with excellent optoelectrical features, high flexibility, and sufficient mechanical stability, have been considered a potential candidate for the use as transparent conductive electrodes. However, ultrathin metal films follow the Volmer–Weber mechanism, resulting in a rough and discontinuous morphology with poor optoelectrical properties due to the bad adhesion to substrates. This review summarizes the progress in strategies for preparing ultrathin and ultrasmooth metal films with superior transmittance and conductivity by successfully suppressing the Volmer–Weber mechanism. The electrical and optical performances of the ultrathin metal films based on improved nucleation processes, as well as applications in ITO‐free organic optoelectronic devices, are also described and discussed in detail. The development of ultrathin metal films with improved metal nucleation processes based on various strategies is summarized in this review. The great progress in the properties of ultrathin metal films as well as their application in indium tin oxide (ITO)‐free organic optoelectronic devices as transparent conductive electrodes are described. [ABSTRACT FROM AUTHOR]

We have demonstrated an indium-tin-oxide free organic light-emitting device (OLED) with improved efficiency by doping poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) with graphene oxide (GO) as a composite anode. In comparison with a pure PEDOT:PSS anode, 55% enhancement in efficiency has been obtained for the OLEDs based on the PEDOT:PSS/GO composite anode at an optimal condition. The PEDOT:PSS/GO composite anode shows a lower hole-injection barrier, which contributes to the improved device efficiency. Moreover, both high transmittance and good surface morphology similar to that of the pure PEDOT:PSS film also contribute to the enhanced efficiency. It is obvious that composite anode will generally be applicable in organic optoelectronic devices which require smooth and transparent anode. [ABSTRACT FROM AUTHOR]

Highlights: [•] An ITO-free flexible OLED with improved efficiency has been fabricated. [•] Template stripping process has been employed to fabricate the ITO-free OLEDs. [•] The smoothness and conductivity of the PEDOT: PSS anode has been improved. [•] The H2SO4 residues on the PEDOT: PSS anode has been eliminated. [•] The device stability has been improved by eliminating the H2SO4 residues. [ABSTRACT FROM AUTHOR]