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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]

As the demand for display technology in consumer electronics and lighting panels increases, thin, light, high‐quality, and more cost‐effective light‐emitting devices are required. Organic light‐emitting devices (OLEDs), satisfying the criteria exactly, have been considered the most promising next‐generation display and lighting technique. In particular, an OLED based on flexible substrate enables the device to be applied to curved displays, electronic newspapers, wearable displays, and conceptual lighting panels, has been always in the spotlight both in science and industry. Great advances on flexible OLEDs (FOLEDs) have been made over the past three decades. The fundamental elements of FOLEDs including substrates, electrodes, fabrication and encapsulation techniques, as well as the strategies of efficiency improvement are discussed herein. Moreover, emerging electrodes such as graphene, carbon nanotubes, metal nanowire network and their composite, flexible perovskite light emitting devices, and stretchable light emitting devices are also considered. Finally, the future challenges and prospects for these devices are put forward. The fundamental elements of flexible organic light‐emitting devices including substrates, electrodes, fabrication and encapsulation techniques, as well as the strategies of efficiency improvement are discussed. Moreover, emerging electrodes such as graphene, carbon nanotubes, metal nanowire network and their composites, flexible perovskite light emitting devices, and stretchable light emitting devices are also considered. Finally, the challenges and prospects for the future are put forward. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An ultrathin Au/graphene composite electrode with high transmittance and conductivity has been demonstrated. • The ultrathin Au/graphene composite electrode is applied to supercapacitor. • Flexible and transparent supercapacitor with the composite electrode exhibits high capacitance and mechanical stability. Abstract Large-area monolayer graphene by chemical vapor deposition as electrode in electronic devices always suffers from shortages of low conductivity and high contact resistance. In this work, we demonstrate a composite electrode by depositing a continuous and homogeneous ultrathin 7-nm Au film on monolayer graphene with low average sheet resistance of 24.6 Ω/□ and high transmittance of 74.6% at 520 nm. The excellent properties of the composite electrode are attributed to the suppressed Au Volmer-Weber growth mode of the ultrathin Au film by the organized hexagonal carbon lattices of graphene. Rigid supercapacitor based on the composite electrode exhibits a capacitance of 81.5 μF/cm2 at the scan rate of 0.1 V/s, which is 17 times higher than the device based on monolayer graphene. Flexible supercapacitor based on the composite electrode can be bending at curvature radius of 2 mm and with slight performance decrease over 1800 bending cycles. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (pero-SCs) possessing high efficiency and low fabrication cost have been considered as the promising wearable energy supply devices in the near future. However, the intrinsic brittleness of the commonly used transparent conducting oxide electrodes is one of the limitations for the mechanical stability of flexible pero-SCs. Here we demonstrate the improved mechanical stability of flexible pero-SCs consisting of ultrathin Au electrode and vapour-deposited perovskite film. The thermal annealing-free perovskite film fabrication by vapour deposition is beneficial to the stability of the ultrathin Au electrode and contributes to the improved mechanical stability of the flexible pero-SCs. The power conversion efficiency for flexible pero-SCs maintains 74% of their initial efficiencies after 2000 bending cycles with a bending radius of 3.5 mm. [ABSTRACT FROM AUTHOR]

Semitransparent perovskite solar cells (PeSCs) with high efficiency and flexibility are demonstrated by using ultrathin Au and dielectric/metal/dielectric multilayered films as bottom and top electrode, respectively. An overall power conversion efficiency (PCE) of 8.67% and an average light transmittance (ALT) of 15.94% in the wavelength range of 500–2000 nm were obtained for the PeSCs. The ALT can be further increased to 31.61% by reducing the thickness of the bottom Au electrode. Furthermore, the PeSCs show excellent flexibility and mechanical robustness, and the PCE maintains 88% of their original efficiencies after 1000 bending cycles with a bending radius of 3.9 mm. [ABSTRACT FROM AUTHOR]

An improved efficiency from an encapsulated flexible top-emitting organic light-emitting device (FTOLED) has been demonstrated by integrating a microstructure onto the polymer encapsulation film. Soft-nanoimprint lithography is employed to integrate the microstructure onto the polymer surface, which enables large area fabrication with high quality, low cost, and repeatable use of the poly(dimethylsiloxane) mold. The light extraction of the FTOLEDs has been improved by integrating the microstructure with two-dimensional tapered micropillars array on the polymer encapsulation film, which can suppress the reflection by enhancing the critical angle of total reflection owing to its gradually changed refractive index. Moreover, the microstructured surface exhibits a hydrophobic property owing to its high contact angle, which results in a self-cleaning ability to protect the FTOLEDs from being polluted by water droplets and dust particles in practical applications. [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]