Silver nanowire (AgNW) electrodes are considered promising candidates for application in flexible optoelectronic devices due to their excellent mechanical flexibility and optoelectrical properties. However, AgNW-based flexible transparent electrodes suffer from critical limitations such as rough surfaces, low adhesion to substrates, poor bending resistance and inferior environmental stability, hindering their industrialized application in flexible optoelectronic devices. In this study, degradable AgNWs composite electrodes with outstanding optoelectrical properties and mechanical stability were fabricated by adopting gum arabic, a natural eco-friendly material, as a modification layer. The composite electrodes exhibit low surface roughness of ∼4.9 nm, sheet resistance of 22 ± 2 Ω sq-1, transmittance of ∼98.3%, exceptional mechanical stability of 200 000 bending cycles and excellent environmental stability of 800 hours storage under ∼80 °C and ∼80% relative humidity. Based on the composite electrode, a flexible green phosphorescent organic light-emitting device achieves a luminance of 55 140 cd m-2 and a current efficiency of 77.4 cd A-1. This research provides a facile and low-cost method for the fabrication of large-area high-performance flexible transparent electrodes.

Quasi-two-dimensional (quasi-2D) perovskites with multi-quantum well structures, large exciton binding energy and high photoluminescence quantum yields represent promising candidates for constructing high-performance perovskite light-emitting diodes (PeLEDs). However, the performance of blue PeLEDs still remains inferior to that of green and red devices due to non-radiative recombination caused by vacancy defects and random phase distribution. Herein, an additive of disodium pyrophosphate was introduced into the precursor solution of blue quasi-2D perovskites to passivate uncoordinated Pb2+ and regulate phase distribution. Defect passivation is achieved through the dynamic coordination of P=O groups to uncoordinated Pb2+ sites. Meanwhile, hydroxyl groups guide the assembly of the perovskite structure by forming hydrogen bonds with halides, which refines the crystallization process and mitigates low-dimensional phases. Consequently, the perovskite films with disodium pyrophosphate exhibit reduced defect density and a homogenized phase distribution, significantly enhancing radiative recombination. The blue PeLEDs with an emission peak at 488 nm achieve a maximum luminance of 6464 cd m(-2) and a maximum external quantum efficiency of similar to 8.8%.

Ultrathin Ag electrodes with the low sheet resistance and high optical transmittance are the candidates for applications in flexible optoelectronic devices. However, the fabrication of ultrathin Ag electrodes with excellent optoelectrical properties and mechanical stability is challenging due to the fact that the ultrathin Ag layer obeys the Volmer-Weber growth mode when the Ag layer is too thin (<10 nm). In this paper, serine (Ser)-mediated anchoring the growth of ultrathin Ag films was proposed by the chemical bonding interactions between the group of -OH in Ser and Ag atoms. The composite transparent electrode of polyethylene terephthalate (PET)/Ser/Ag (7 nm)/MoO3 (20 nm) possesses a low sheet resistance of similar to 8.5 Omega/sq, a high optical transmittance of similar to 87.2 % at 550 nm and the robust mechanical stability of 100,000 bending cycles at a bending radius of 5 mm. The excellent performance can be attributed to the formation of Ag-O bonds during the growth procedure of Ag films, resulting in the uniform growth of Ag films and outstanding adhesion to substrates. Flexible organic lightemitting devices were constructed based on the composite transparent electrodes, achieving a maximum luminance of similar to 14070 cd/m(2) and a maximum current efficiency of similar to 7.5 cd/A.

Flexible optoelectronic devices play a crucial role in the field of wearable electronics. However, their potential and development have been hindered by the lack of high-performance, durable, and flexible ultrathin Ag mesh electrodes using a direct writing technique by a Chinese brush. Through precise control over the writing process, the printed Ag mesh with an ultrathin thickness of similar to 100 nm and a high width resolution of similar to 20 mu m was achieved. The resulted composite (PEDOT:PSS) possess a low sheet resistance of similar to 12 Omega/sq and a high transmittance of similar to 91%. Benefiting from the ultrathin Ag mesh and embedded structure, the composite electrode shows the quite low surface roughness (similar to 0.9 nm), along with exceptional mechanical flexibility with a micrometer-scale bending radius. Furthermore, stretchable organic light-emitting devices (OLEDs) based on this composite electrode present an impressive current efficiency of 88.6 cd/A. Significantly, the OLEDs remain 86% initial current efficiency over 1000 bending cycles and maintain 88% initial luminance at the 50% strain. Interestingly, this direct writing technique possesses the remarkable capability to print transparent electrodes on curved or uneven substrate surfaces, expanding its potential for universal applications. This work presents a straightforward and general printing method for constructing high-performance flexible transparent electrodes for various flexible electronics.

Flexible fabric-based top-emitting organic light-emitting devices (Fa-TEOLEDs) have garnered significant attention due to their tremendous potential in wearable electronics. However, fabricating cost-effective high- quality metal reflection electrodes on fabric still poses a formidable challenge. Herein, flexible fabric-based Ag reflection electrodes, which possess a sheet resistance of similar to 0.15 Omega/sq and a reflectance of similar to 94.7 %, along with excellent environmental and mechanical stability, were fabricated through the innovative combination of fast silver mirror reaction and template-stripping processes. Adopting the fabric-based Ag electrodes, ultra-flexible red, green and blue Fa-TEOLEDs with ultrathin emitting layers present the remarkable current efficiencies of 39.4 cd/A, 119.0 cd/A and 44.8 cd/A, respectively. Impressively, the Fa-TEOLEDs show excellent mechanical flexibility and durability, retaining similar to 88.1 % of the original luminance after 700 bending cycles at a bending radius of 2 mm. This substantial advancement marks a crucial stride forward in the design of high-quality metal reflection electrodes and the advancement of Fa-TEOLEDs for wearable electronics.

The progress of stretchable organic light-emitting devices (OLEDs) has brought about new possibilities for highly functional wearable electronics. However, the efficiency and durability of stretchable OLEDs have been limited by the performance of stretchable transparent electrodes. Here, we proposed an interface engineering strategy that involves anchoring the growth of silver (Ag) atoms with amine-enriched biomaterials for high-quality stretchable transparent electrodes. The strong interactions between the Ag atom and the amine group enable the uniform Ag electrodes at an ultralow thickness of 7 nm, and provide remarkable mechanical flexibility and strain endurance to the Ag electrodes. The distinct effects of different amino acids were investigated, and a deep understanding of their unique contributions to the film formation process was gained. The resulting ultrathin Ag electrodes exhibit outstanding optoelectrical properties (transmittance of 98

Flexible organic light-emitting devices (OLEDs) are emerging as a cutting-edge technology that revolutionizes displays and lighting panels to be lightweight, bendable, foldable, and even stretchable. However, they suffer from the poor light outcoupling efficiency due to the presence of various optical losses. Herein, a novel method of optical manipulation is proposed, which involves incorporating light-scattering titanium oxide (TiO2) nanoparticles (NPs) into flexible substrates, along with imprinting random micro-lens arrays (RMLA) at the bottom of the substrates. Adopting the light outcoupling structures, the flexible single white OLEDs demonstrate a substantial improvement of 95.6% in the external quantum efficiency (EQE) compared to conventional flexible OLEDs, while maintaining a desirable spectral profile without any distortion. To further improve the optoelectronic performance, the light outcoupling structures are adopted in flexible tandem white OLEDs with two emission units, the maximum current efficiency is 147.8 cd A-1, and the maximum EQE comes to 46.2%, which is 1.74 times higher than that of the flexible single OLEDs with the same light outcoupling structures. This work offers a convenient way to design flexible light extraction substrates for efficient wearable electronics. This work demonstrates efficient flexible white organic light-emitting devices (OLEDs) by introducing the light out-coupling structures of incorporating light-scattering TiO2 nanoparticles into flexible substrates and imprinting random micro-lens arrays at the bottom of the substrates. The flexible tandem white OLEDs possess a current efficiency of 147 cd A-1, a power efficiency of 77.4 lm W-1 and an external quantum efficiency of 46.2% without spectrum distortion. image

Silver nanowire (AgNW) transparent electrodes are considered as a promising candidate for applications in flexible optoelectronic devices. However, it remains a great challenge to obtain flexible AgNW electrodes with excellent optoelectrical properties and mechanical flexibility. Here, highly stable Ag nanoparticle (AgNP)-enhanced plasmonic AgNW electrodes are demonstrated via the controllable in situ growth of AgNPs at the AgNW junctions and introduction of an L-histidine (L-His) wrapping layer. The flexible transparent electrodes of AgNW-AgNP/L-His possess a low sheet resistance (R-sh) of similar to 17.5 Omega sq(-1), a high transmittance of similar to 92.5% (550 nm), and a robust mechanical stability (100,000 bending cycles). Benefiting from plasmon-coupling effects, flexible polymer light-emitting devices (FPLEDs) with AgNW-AgNP/L-His electrodes present a current efficiency (CE) of similar to 14.8 cd A(-1) and an external quantum efficiency (EQE) of similar to 5.6%, constituting similar to 80% and similar to 75% increases compared to those of the reference devices with AgNW electrodes, respectively. Additionally, the laminated flexible transparent PLEDs (FT-PLEDs) are demonstrated by integrating polydimethylsiloxane/AgNW-AgNP anodes by a soft lamination process. The FT-PLEDs present a CE of similar to 7.1 cd A(-1) (cathode side: similar to 3.9 cd A(-1); anode side: similar to 3.2 cd A(-1)) and an EQE of similar to 2.7% (cathode side: similar to 1.5%; anode side: similar to 1.2%). Furthermore, the FPLEDs and FT-PLEDs exhibit robust mechanical durability, maintaining similar to 89% and similar to 86% of their initial luminance after 1000 bending cycles at a bending radius of 2 mm, respectively. This work opens up a new avenue for the development of high performance and stable flexible optoelectronic devices.

Low-cost fabric-based top-emitting polymer light-emitting devices (Fa-TPLEDs) have aroused increasing attention due to their remarkable potential applications in wearable displays. However, it is still challenging to realize efficient all-solution-processed devices from bottom electrodes to top electrodes with large-scale fabrication. Here, a smooth reflective Ag cathode integrated on fabric by one-step silver mirror reaction and a composite transparent anode of polydimethylsiloxane/silver nanowires/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) via a water-assisted peeling method are presented, both of which possess excellent optoelectrical properties and robust mechanical flexibility. The Fa-TPLEDs are constructed by spin-coating functional layers on the bottom reflective cathodes and laminating the top transparent anodes. The Fa-TPLEDs show a current efficiency of 16.3 cd A-1 , an external quantum efficiency of 4.9% and angle-independent electroluminescence spectra. In addition, the Fa-TPLEDs possess excellent mechanical stability, maintaining a current efficiency of 14.3 cd A-1 after 200 bending cycles at a radius of 4 mm. The results demonstrate that the integration of solution-processed reflective cathodes and transparent anodes sheds light on a new avenue to construct low-cost and efficient fabric-based devices, showing great potential applications in emerging smart flexible/wearable electronics.

Flexible transparent electrodes (FTEs) possess excellent optoelectrical properties, mechanical robustness, and environmental adaptability are important for the industrial scale development of flexible electronics. Silver nanowires (AgNWs) are widely used in FTEs owing to their excellent optoelectrical properties and mechanical flexibility. However, the high surface roughness and poor stability of AgNWs FTEs still limit their practical applications. Here, highly stable FTEs are demonstrated via combining AgNWs and biomaterial propolis which is eco-friendly and antioxidative. The AgNWs/propolis composite transparent electrodes exhibit excellent optoelectrical performance as well as a smooth surface (root-mean-square roughness ∼ 6.2 nm). Meanwhile, the composite electrodes possess high mechanical stability (10,000 bending cycles), thermal stability, and environmental adaptability (60 °C and 85 ± 3% humidity for 700 h). The versatile composite FTEs show great potential applications in organic light-emitting diodes and pressure sensors, which exhibit high performance, mechanical stability, and environmental adaptability. Our strategy of introducing biocompatible materials into metallic nanowires opens up new possibilities to achieve high-quality FTEs in a simple and eco-friendly way.

For the tandem organic light emitting diodes (TOLEDs) with the charge generation unit (CGU) of LiF/Al/MoO3, there is a significant current lateral spreading causing light emission over an extremely large area outside the OLEDs pixel, due to the conductive interfacial layer caused by the oxidation-reduction reaction between Al and MoO3 layers. To crack this nut, a buffer layer of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) is inserted between Al and MoO3 layers. The result shows the HAT-CN buffer layer eliminates the spread light emission in the TOLEDs. What's more, the device characteristics show the new CGU of LiF/Al/HAT-CN/MoO3 has stronger charge generation and injection capabilities. The white TOLEDs with the new CGU exhibit a high external quantum efficiency (EQE) of 28.4%. Compared with the single OLEDs and the TOLEDs with the CGU of LiF/Al/MoO3, the efficiency is increased by 143% and 44%, respectively.

The performance of polymer light-emitting diodes based on poly(9,9-dioctylfluorene) (PFO) is strongly affected by the presence of beta-phase in the polymer films. In this work, beta-phase PFO films were developed by a facile method dip-coating in one step. Absorption spectra with an additional peak at 435 nm and red-shifted emission spectra demonstrate the formation of beta-phase in the dip-coated films. Notably, beta-phase content in the PFO films can be tailored by controlling the withdrawal speed. The experimental results show that the content of beta-phase in PFO films increases from 1.4 % to 23.2 % with the decreasing of the withdrawal speed from 60 mm/min to 5 mm/min, and the device efficiency and color purity for the blue emission get improved due to the formation of beta-phase. When the withdrawal speed is 5 mm/min, the devices possess the optimal performance with a current efficiency of 2.47 cd/A, which is 3.6 times as high as that of the device with the spin-coated PFO film as emitting layer. These results demonstrate that as a simple methodology, the dip-coating technology can effectively induce the molecular chain orientation in the film to regulate the optoelectronic properties for applications in efficient optoelectronic devices.

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)/MoO3 (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.

White and RGB phosphorescent OLEDs were constructed by continuously brush-coating the hole-injection layer and small molecule light-emitting layer.

The mismatch of refractive index at the interfaces of substrate, electrode/organic material will cause nearly 80% light losses in the organic light-emitting device (OLED). To solve this problem, a light extraction layer with random corrugated structures is fabricated with a quite simple method to enhance the light out-coupling efficiency of OLED. Compared with the planar OLED, about 21% enhancement of current efficiency is achieved in the corrugated OLED. This improvement comes from the scattering effect of polymer phase separation film, which can suppress surface plasmon polariton losses and reduce waveguide mode optical losses. In addition, the structures can decrease the angular dependence of the emission spectra in the planar OLED. With these advantages, the random corrugated structures provide the potential to be applicable to OLED for high-efficiency lighting and full-color display.

Efficient electron injection from cathode to electron transport layer is generally required to realize high-performance inverted organic light-emitting devices (IOLEDs). In this work, highly efficient IOLEDs are developed by employing a non-doped charge-generation unit of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/Al/LiF as electron-injection layers (EILs). The ultraviolet photoelectron spectroscopy (UPS) shows that the insertion of HAT-CN layer reduces the work function of EILs by 0.21 eV. Combined with the currentvoltage characteristics of electron-only devices, the role of the HAT-CN layer in promoting electron injection is confirmed. What's more, the double EILs device with Rubrene as a probe verifies the strong hole blocking ability of HAT-CN/Al/LiF. Based on the EILs, the inverted blue phosphorescent OLEDs with a maximum current efficiency of 29.4 cd/A are realized. The excellent performance proves the superiority of HAT-CN/Al/LiF as EILs.

An efficient CGU is applied to the high efficiency super-flexible white TOLEDs, which show a higher PE than the single OLEDs. After being bent for 3000 cycles, the devices retain ∼90% of the original luminance.

To cut cost and improve device performance, expensive and acidic hole transport material (HTM) PEDOT:PSS is replaced by copper(I) thiocyanate (CuSCN) and NiO x in solution‐processed white organic light‐emitting diodes, respectively. However, the luminescence quenching caused by interfacial defects on the surfaces of CuSCN and NiO x limits the devices’ full potential. To crack the nuts, an ultrathin graphene oxide (GO) layer is inserted between hole transport layer (HTL) and emitting layer (EML) as a passivation layer. The time‐resolved photoluminescence spectra of EML intuitively prove the inhibitory effect of GO on exciton quenching. What is more, the ultraviolet photoelectron spectroscopy and impedance spectroscopy reveal that the ultrathin GO layer can also increase the work function of HTM and promote hole injection. Relative to the devices without a GO layer, the efficiency of CuSCN/GO‐containing device is enhanced from 18.1 cd A −1 (6.6 lm W −1 ) to 30.3 cd A −1 (19.8 lm W −1 ), and the device with NiO x /GO achieves an enhancement of power efficiency by 98%, from 10.1 to 20.0 lm W −1 .

Inverted organic light-emitting diodes (IOLEDs) can be integrated with low-cost n-channel thin-film transistors for use in active-matrix OLEDs (AMOLEDs). However, the electron injection from conventional indium tin oxide (ITO) cathode to the upper electron transport layer usually suffers from a large injection barrier. To improve the electron injection efficiency, the electron injection layers (EILs) of ZnO modified by a self-assembled monolayer arginine (Arg) were developed to construct efficient IOLEDs. ZnO/Arg EILs present an ultralow work function (WF) of 2.35 eV, which is lower than that of ZnO modified by poly(ethylenimine) (PEI) (2.77 eV). The mechanism of low WF is attributed to the generation of strong molecular dipoles and interface dipoles at the interface of ZnO/Arg. The green fluorescent IOLEDs with ZnO/Arg present a low turn-on voltage (Von) of 3.5 V and a maximum current efficiency (CEmax) of 4.5 cd/A. Especially, the device possesses a half-life of 3600 h at an initial luminance of 1700 cd/m2, which is 36 times as long as that of the IOLEDs with ZnO/PEI as EILs. Furthermore, the green phosphorescent IOLEDs show a Von of 3.5 V, a CEmax of 59.1 cd/A, and a maximum external quantum efficiency (EQEmax) of 16.8%. At a luminance of 10 000 cd/m2, the efficiency roll-off of the device is only 6.3%.

Pyrochlore-type (Ca,Ti)(2)(Nb,Ti)(2)O-7 thin films have been grown on single-crystalline LaAlO3 and yttria-stabilized zirconia substrates by a magnetron sputtering system. Atomic-scale interface structure and growth mode of the (Ca,Ti)(2)(Nb,Ti)(2)O-7 films on the substrates with different crystal structures have been investigated by advanced electron microscopy techniques. In both hetemsystems, the film/substrate orientation relationship of [100] (001)(film)//[100](001)(substrate )has been determined. In the heterosystem of (Ca,Ti)(2)(Nb,Ti)(2)O-7/yttria-stabilized zirconia, the films directly grow on the substrates. In contrast, in the (Ca,Ti)(2)(Nb,Ti)(2)O-7/LaAlO3 hetemsystem, a perovskite-type Ca1-square(Ti,Nb)O-3 interlayer with a few unit cells in thickness forms at the interface and interfacial reconstruction occurs at the (Ca,Ti)(2)(Nb,Ti)(2)O-7/Ca1-square(Ti,Nb)O-3 interface. Our findings indicate that the formation of the interlayer and the (Ca,Ti)(2)(Nb,Ti)(2)O-7/Ca1-square(Ti,Nb)O-3 interface reconstruction can accommodate the film/substrate dissimilarities in the crystal structures and facilitate the growth of single-crystalline pyrochlore-type films on the perovskite-type substrates.