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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]

The next generation of optoelectronic devices requires transparent conductive electrodes to be flexible, inexpensive and compatible with large scale manufacturing processes. We report an ultrasmooth, highly conductive and transparent composite electrode on a flexible photopolymer substrate by employing a template stripping method. A random silver nanowire (AgNW) network buried in poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film constituted the composite electrode. Besides the effectively decreased surface roughness, its sheet resistance and transmittance are comparable to those of conventional PEDOT:PSS electrode. As a result, the efficiency of the OLEDs based on the composite electrode exhibited 25% enhancement compared to the OLEDs with conventional PEDOT:PSS electrode. Moreover, the performance of the flexible OLEDs remains stable after over one hundred bending cycles. [ABSTRACT FROM AUTHOR]

We propose a plasmonic ultrathin metal grid electrode as a promising light outcoupling strategy in a flexible organic light-emitting device (OLED). The plasmonic ultrathin metal grid electrode consists of an ultrathin Au grid film incorporating with plasmonic subwavelength corrugations, which was fabricated by lithography and nanoimprint technologies, demonstrates excellent optical and electrical properties as the substitute of ITO transparent electrode in flexible OLED. The transmittance of the plasmonic ultrathin Au grid electrode is 88.5% at 550 nm and the sheet resistance is about 36 Ω/sq. The periodic subwavelength corrugations of the plasmonic ultrathin Au grid electrode excite the surface plasmon-polariton (SPP) resonance which is an adverse optical mode with power loss in OLED, and the photons trapped in SPP mode are effectively outcoupled and extracted by the plasmonic corrugations. Compared to the ITO-based device, OLED based on plasmonic ultrathin Au grid electrode realizes a desirable enhancement of 60.3% in current efficiency. In addition, the flexible OLED based on the proposed electrode also exhibits decent mechanical robustness and flexibility with stable electroluminescence performances. Image 1 • A plasmonic ultrathin metal grid film incorporating with corrugations is reported. • The proposed electrode serves as a light extraction strategy in flexible OLED. • A 60.3% enhancement in current efficiency has been achieved. [ABSTRACT FROM AUTHOR]

Instability and large wire-wire contact resistance of silver nanowires (AgNWs) have seriously hindered their practical applications as electrodes in optoelectronic devices. Although various methods have been demonstrated to improve the stability and conductivity of the AgNWs, a simple and low-cost process, especially compatible to the flexible substrates for their applications in flexible devices, is still a challenge. Here, perfluorinated sulfonic acid (PFSA) polymer has been employed as a surface-passivation layer on the AgNWs through a simple surface coating. The PFSA passivation can simultaneously improve the conductivity, thermal stability and mechanical stability of the AgNWs. As a result, the PFSA-passivated AgNWs film maintains an almost constant conductivity under ambient condition after heating for 30 min at 250 °C or 10 days storage at room temperature, and 600 continuous bending cycles at a bending radius of 1 mm. The PFSA-passivated AgNWs have been applied to flexibly organic light emitting devices as their electrodes, and both mechanical stability and long-term operational stability have been improved. Image 1 • Simultaneous improvement of conductivity, stability and flexibility. • Excellent thermal and chemical durability. • Suitable for fabricating flexible OLEDs. [ABSTRACT FROM AUTHOR]