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Organic single crystals are highly promising for applications in optoelectronic devices because of their higher mobility and thermal stability than amorphous thin films. Although white organic single crystals have been fabricated by the double-doped method and applied to realize white organic light‐emitting devices (WOLEDs), the unbalanced carrier transport properties of the unipolar crystals severely limit the device performance. Here, ambipolar white organic single crystals are obtained by using mixed p- and n-type molecules as an ambipolar host for the red and green dopants. The white crystal with balanced carrier transport and balanced blue, green, and red emission intensity was applied to the single-crystal WOLEDs. The highest brightness of 1956 cd m−2 and the current efficiency of 1.31 cd A−1 are achieved, which are the best performance of the single-crystal WOLEDs reported to date. A high color rendering index is obtained, which varies between 82 and 87 with increasing driving current. It is expectable that this strategy would support the practical applications of organic single crystal-based OLEDs. [ABSTRACT FROM AUTHOR]

The rapid development of nanotechnology for the last 30 years has enabled a rapid expansion in the applications of functional nanoparticles (NPs) on optoelectronic devices. Especially, NPs are of high significance in organic light‐emitting diodes (OLEDs) as they provide feasible solutions to the enduring challenges related to higher device efficiency. The use of NPs with designed structure and functionality is demonstrated, indicative of their great application potentials in OLEDs. Herein, the recent advances in OLEDs with the utilization of functional NPs are summarized. Starting with a brief overview about the unique properties of NPs, comprehensive roles of NPs in OLEDs, which include improving carrier injection abilities, local surface plasmonic resonance, light scattering, and magnetic field effects, are discussed together with their latest research progresses. Furthermore, one‐component and multicomponent heterostructured NPs with multifunctional capabilities in OLEDs are overviewed. Following the summarization of the roles of NPs in OLEDs and their latest research progress, a brief conclusion and outlook regarding the future research directions of highly efficient OLEDs by incorporation of NPs are provided. [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]

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]