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Wide applications of smart wearable electronics have triggered tremendous needs for energy storage devices featuring lightweight, transparency, foldability and breathability. However, conventional supercapacitor electrodes are always substrate-supported with a compact film structure, which strongly limits their air permeability, flexibility and transparency. In this report, we demonstrate the use of a freestanding, ultrathin (∼ 6 μm), highly conductive (4 × 105 S/m), highly transparent (> 91%), air permeable (2600 mm/s at 10 Pa) and foldable metallic mesh electrode, decorated with active MnO2 microstructures, as a breathable, transparent and foldable supercapacitor electrode. By introducing Au nanoparticles as the “nanoglue” between Ni and MnO2, excellent electrochemical performances including large areal capacitance (268 mF/cm2) and high cycling stability (90.1% capacitance retention after 10000 cycles) are obtained in the MnO2-Au-Ni mesh electrode. Furthermore, the assembled all-solid-state supercapacitor device delivers high optical transparency (∼83.6%), high air permeability (45.4 mm/s at 100 Pa), superior electrochemical performances and can withstand various deformations including bending, folding, and crumpling. The present freestanding mesh structure electrode could be further explored and applied in more potential applications, such as ion batteries, wearable sensors, and conformal healthcare devices.

Engineered particle-doped light diffuser is realized by a simple, low-cost soft lithographic method. A flexible photopolymerizable mold is employed as an intermediate transferring template directly from the developed photoresist texture to fabricate engineered particle-doped light diffuser. The well-designed surface microstructure can directionally scatter the incident light, while the doped ultra-violet curable resin with low concentration of the 2 μm-diameter organosilicone particles can homogenize the scattering light without decreasing transmittance. Experimental results show that the measured transmittance can be as high as 96.9% with little backscattering effect over the whole visible regime. Meanwhile, the haze raises from 30% to 75% with increased dopant concentration from 1 wt% to 7 wt% and thickness of the residual layer from 10 μm to 40 μm remained in the imprinting process. The proposed engineered particle-doped light diffuser can manage scattering angle, luminance uniformity and haze, thus it has the capability of homogenizing light and eliminating striations to create more visually pleasing structured lighting in commercial and residential environments. We anticipate that the approach appears to be a strong candidate for future development because of its scalable nature, environmentally-friendly process and relatively low cost.

A novel approach to fabricate large-scale embedded metallic mesh transparent conductive electrodes (TCEs) on flexible substrates via a low-cost and facile selective electrodeposition process combined with inverted film-processing methods is proposed for the first time. The optimized embedded Ni mesh TCEs on polyethylene terephthalate (PET) exhibit excellent optoelectronic properties (Rs ∼ 0.2 Ω sq−1 & T ∼ 84%), high figure of merit (FOM ∼ 1.0 × 104) and mechanical durability properties, which arise from the embedded inverted T-type shape of the electrodeposited Ni mesh. The resultant embedded Ni mesh/polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid electrodes are utilized both as current collectors and active electrode materials for all-solid-state flexible transparent supercapacitors, which show high transparency, superior electrochemical performances, excellent mechanical flexibility and high capacitance retention. Even after 1000 cycles of repetitive bending with a radius of 2 mm, the capacitance exhibited a decrease within only 5.2%. The high performance can be attributed to the excellent optoelectronic properties of embedded Ni mesh electrodes in combination with superior electrochemical properties of PEDOT:PSS. This provides a simple, cheap and controllable method for fabricating high-performance flexible TCEs and thus constructing flexible and transparent energy conversion and storage devices and systems.

Holography metasurfaces have been used to control the propagation of light to an unprecedented level, exhibiting the immense potential for light steering in organic light-emitting diodes (OLEDs). Here, a new approach to tailoring directive gain for high contrast, wide-viewing-angle OLEDs is proposed by implementing a spcekle image holography (SIH) metasurface. The experimental and theoretical results provide the direct proofs that the SIH metasurface can play very important roles not only in releasing the trapped energy flow insides the devices but also in tailoring the wavefronts to the preferred patterns due to its "regional orientation" k-vectors patterns. The resulting power efficiency and external quantum efficiency of the OLEDs using a SIH metasurface are 1.97 and 1.95 times that of the reference device with a standard architecture. Furthermore, the wavefronts of emitted light are delicately modulated in a polarization-independent manner, yielding 2.5 times higher contrast ratio compared to the reference device. This unique engineered directive gain property is also well-retained for the viewing angles varing from normal to titled ±60° without spectral distortion. These results enrich the understanding of light wavefronts control in OLEDs and highlight its potential application in display as well as light steering for other optoelectronics.

We design and numerically investigate an optical absorber consisting of the sub-wavelength dielectric grating covered by continuous thin aluminum film. In this absorber, the aluminum film act as an efficient absorbing material because of the enhanced electric field in the air nano-grooves, and the absorption spect+rum can be manipulated by Fabry-Perot cavity mode resonance. According to the spectrum manipulation mechanism, the wavelength of absorption peak can be tuned by changing the heights and widths of the air nano-grooves. More importantly, the high absorption is very robust to the incident angle around the designed wavelength. From the nanofabrication point of view, the light absorber can be fabricated more easily without the need for ion or electrochemical etching of metal and it is easy to be integrated into complex photonic devices.

An optical absorber with the advantages of flexibility, broadband, insensitivity to incident angle and high efficiency in double-sided incidence is studied, realized and characterized. The absorber is composed of the tapered concave nanostructure covered with thin Ni-SiNx film. Simulation results show that there exist two different mechanisms in the absorptive behavior. The absorption is measured as 94.2% and 93.9% from 400 nm to 1600 nm in the front- and back-sided incidence, respectively. The absorber is fabricated by economic process, thus it can have a variety of potential applications, such as solar–thermal energy harvesting, thermal radiation detection, etc.

High-performance light absorption devices have previously been obtained by coupling photons to conduction electrons. However, energy harvesting is limited in these devices because they only absorb light from one incident direction. We have developed a wide-band bidirectional visible light absorber (BLA) based on a quasi-periodic nanocone array coated with a dielectric-loaded Au monolayer. The proposed BLA is capable of simultaneously absorbing light from both the front and rear surfaces, yielding an average front absorption of 87.4% and a corresponding rear absorptivity of 76.2% in the range 300–700 nm. The bidirectional absorption properties were obtained at incident angles varying from 0 to 60°. Experimental and theoretical analyses indicate that these absorption properties can be ascribed to a combination of the localized cavity resonant mode, the localized surface plasmonic mode, the guided mode resonance, and hybrid coupling between the cavity resonant mode and the surface plasmonic mode. This concept provides a new pathway for the fabrication of new types of flexible or wearable solar thermoelectric devices, photodetectors, or other solid-state devices with large areas.

Sub-wavelength antireflective structures are fabricated by using a soft roll-to-plate nanoimprinting lithography. The proposed methodology employs a modified polyurethane acrylate as a flexible mold due to its high resolution, chemical inertness, polymerization characteristics, and its non-wetting, very low surface energy. Large-format (750mm x 750mm) plastic film with the recombined double-sided sub-wavelength structures is obtained, which has fascinating broadband antireflective effect. The roll-to-plate ultra-voilet nanoimprinting provides the capability of patterning sub-100nm structures, a short period of process time and allows the fabrication of sub-wavelength structure on a large number of flexible or rigid substrates in an economic fashion.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2660 wileyonlinelibrary.com efforts devoted to the development of high-performance phosphorescent or thermally activated delayed fl uorescent emitters and novel device architectures, internal quantum effi ciency has already achieved ≈100% for energy conversion due to the fully use of both singlet and triplet states. [ 6–8 ] Unfortunately, one of the major drawbacks of conventional OLEDs is the light confi nement that a high fraction of energy fl ow generated in the emissive materials is trapped as substrate, waveguide (WG), and surface plasmon polariton (SPP) modes in glass substate, organic/transparent indium-tin-oxide (ITO) layers, and metallic rear electrode due to the mismatch of refractive indices in the fl at multilayered structures. [ 9–11 ]

Flexible organic light-emitting diodes are gaining increasing importance as a leading technology for high-quality displays and lighting in wearable electronics due to their low power consumption, excellent color gamut, and the desirable mechanical flexibility with soft materials and curvilinear surfaces. However, further enhancements in efficiency are still challenging because of the optical confinement and limited light out-coupling efficiency. Here, a simple and wavelength-independent light extraction scheme is demonstrated using the biomimetic quasirandom nanostructures that can simultaneously enhance the out-coupling of the waveguided light and allow the minimized ohmic losses without spectral distortion. Compared to periodic grating structures, the nanoimprinted quasirandom nanostructures can broaden the periodicity and randomize the emission directionality, leading to the superiority of color stability over the visible wavelength range for a large variation of viewing angles. The resulting external quantum efficiency and current efficiency are 1.51 and 1.43 times that of a conventional flexible organic light-emitting diode used as a comparison, respectively.

An efficient tandem organic light-emitting diode is realized by employing a novel light out-coupling structure with deterministic quasi-periodic nanocone arrays. The enhancement of color spatial uniformity and operational stability is simultaneously realized along with the remarkable efficiency improvement in tandem devices by integrating multi-photon emission and light out-coupling techniques. The optimized tandem organic light-emitting diode with two emission units exhibits an enhancement factor of 4.99 and 10.49 for device efficiency and half-decay lifetime, respectively, as compared to the conventional device with a planar single-unit structure. Moreover, it is verified that the emission color with viewing angles was significantly stabilized with no apparent spectral distortion. Theoretical calculations clarify that the improved device performance is primarily attributed to the effective extraction of the waveguide and surface plasmonic modes of the confined light over all the emission wavelengths and viewing-angles.

Highly power-efficient white organic light-emitting diodes (OLEDs) are still challenging to make for applications in high-quality displays and general lighting due to optical confinement and energy loss during electron-photon conversion. Here, an efficient white OLED structure is shown that combines deterministic aperiodic nanostructures for broadband quasi-omnidirectional light extraction and a multilayer energy cascade structure for energy-efficient photon generation. The external quantum efficiency and power efficiency are raised to 54.6% and 123.4 lm W−1 at 1000 cd m−2. An extremely small roll-off in efficiency at high luminance is also obtained, yielding a striking value of 106.5 lm W−1 at 5000 cd m−2. In addition to a substantial increase in efficiency, this device structure simultaneously offers the superiority of angular color stability over the visible wavelength range compared to conventional OLEDs. It is anticipated that these findings could open up new opportunities to promote white OLEDs for commercial applications.

Color filter incorporating a subwavelength triangular-lattice cylinder arrays in metal-dielectric films on quartz substrate was proposed. The device consists of a quartz substrate, a triangular-lattice cylinder arrays in both dielectric layer of ZnS and a metallic layer of aluminum (Al). The broadband transmission characteristic of the proposed device in the visible wavelength range was investigated in detail by the rigorous coupled wave analysis (RCWA). Specially by discussing the effects of the structure parameters to the resonant wavelength, typical optimized structure parameters are obtained, in which more than 74.6% peak transmission efficiency with FWHM of ~ 80 nm were simultaneously achieved for the tricolor filters. The simulation results show that the peak transmission efficiency (PET) increases more than 17% with lower color cross-talk compared to the previous color filters.

We numerically and analytically report an ultra-broadband near perfect absorber based on one-dimensional metal-dielectric-metal grating at visible light for TM polarization. A unit cell of this design is composed of metal-dielectric-metal grating, where the bottom metallic layer and the upper metallic coating are separated from each other by the intermediate dielectric grating. The absorber exhibits an average absorption of over 90% in the range 400-700nm. Moreover, they remain very high over a wide range of incident angle up to 45°.The electromagnetic field distributions are investigated, which reveals that this broadband absorption behavior is ascribed to the combination of surface plasmon resonance and cavity resonance. Furthermore, impedance calculations were carried out to explain the absorption behavior. The ultra-broadband near-perfect angle-robust absorber can be a good candidate for many fascinating applications, including solar-energy harvesting as well as producing artificial colors on a large scale substrate.

Conventional fabrication methods for realization of metal mesh (MM) based transparent conductive film (TCF) are not economic and environmentally friendly. By combination of the scrape and selective electroplating techniques, a vacuum sputtering/evaporation-free process is explored for fabrication of high-performance MM based TCF. The fabricated TCF exhibits ultra-low sheet electrical resistance (Rs = 0.07 Ω sq-1) at average transmittance of 83% in visible region. The sample cannot only exhibit high heating temperatures (140 °C) at low input voltage (1.5 V) with fast and stable thermal response but provide high electromagnetic interference shielding efficiency (EMI SE) more than 43 dB in X-band. The processing chain provides a robust, powerful and scalable platform, which may open up a new avenue for realizing multifunctional TCF in diverse applications.

With the demanding requirements for light source, light emitting diodes (LED) attracts more and more attention because of its inherent advantages such as low power consumption, high reliability and longevity. However, there are two disadvantages for LED, one is the low light extraction efficiency resulting from the total internal reflection, and the other is the relative large scattered angle. In order to improve the light extraction efficiency and collimate the out-coupling light, a sub-micron Fresnel lens array is introduced and investigated in this paper. The focal length of the proposed Fresnel lens is 3μm and the minimum width of the outmost ring is about 150nm. To calculate and analyze the light extraction efficiency and the scattered angle of LED with such Fresnel lens array structure, we optimize the parameters of the Fresnel lens, such as the depth of the Fresnel lens array structure and the thickness of the p-type gallium nitride layer by using the finite difference time domain method (FDTD). By comparing the discussed patterned GaN-based LED with that traditional flat LEDs, it can be found that significant enhancement factor of the light extraction efficiency, which is improved by 3.5 times, can be obtained and the scattered angle at half maximum can be decreased 50° from 60° with this novel Fresnel lens structure. It will be expected that the proposed sub-micron structure can find wide applications in LEDs industry. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We propose nano-meanders that can achieve wide-angle band absorption in visible regime. The nano-meander consists of a subwavelength dielectric grating covered by continuous ultra-thin Aluminum film (less than one tenth of the incident wavelength). The excited photonic resonant modes, such as cavity mode, surface plasmonic mode and Rayleigh-Wood anomaly, are discussed in detail. Nearly total resonant absorption due to funneling mechanism in the air nano-groove is almost invariant with large incident angle in transverse magnetic polarization. From both the structural geometry and the nanofabrication point of view, the light absorber has a very simple geometrical structure and it is easy to be integrated into complex photonic devices. The highly efficient angle-robust light absorber can be potential candidate for a range of passive and active photonic applications, including solar-energy harvesting as well as producing artificial colors on a large scale substrate.

Broadband metamaterial absorber (MA) in the whole visible regime has attracted an enormous amount of attention for its potential applications in thermophotovoltaic cells, thermal emitters, and other optoelectronic devices. Nonetheless, complicated device configuration is still involved in achieving broadband, polarization-independent MA and it results in a cost-ineffective fabrication process. In this paper, a novel MA composed of a periodic array of dielectric cylinder sandwiched by the non-noble metal of nickel (Ni) film is demonstrated. Experimental results show that the proposed MA exhibits strong absorptive behavior independent of polarization in the whole visible regime (400-700 nm). The absorption still remains 80% when the incident angle is 60°. The proposed fabrication method is well compatible with the conventional soft nano-imprinting lithography technique, thus it is economic and scalable for a large-format substrate. These results provide an alternative method for the realization of high-performance visible light absorber and offer new opportunities for potential applications in related fields.

Because of their mechanical flexibility, organic light-emitting diodes (OLEDs) hold great promise as a leading technology for display and lighting applications in wearable electronics. The development of flexible OLEDs requires high-quality transparent conductive electrodes with superior bendability and roll-to-roll manufacturing compatibility to replace indium tin oxide (ITO) anodes. Here, we present a flexible transparent conductor on plastic with embedded silver networks which is used to achieve flexible, highly power-efficient large-area green and white OLEDs. By combining an improved outcoupling structure for simultaneously extracting light in waveguide and substrate modes and reducing the surface plasmonic losses, flexible white OLEDs exhibit a power efficiency of 106 lm W(-1) at 1000 cd m(-2) with angular color stability, which is significantly higher than all other reports of flexible white OLEDs. These results represent an exciting step toward the realization of ITO-free, high-efficiency OLEDs for use in a wide variety of high-performance flexible applications.

Autostereoscopic displays are a promising three dimensional display technology for its convenience and compatibility with current display systems which has attracted considerable attention. We describe in detail an autostereoscopic display system with full-parallax using a directional light-guide device with continuously variable spatial frequency sub-micron grating structures. The optimization process of parameters of the multi-direction light-guide is given. A method of implementing sub-micron grating pixels (SMGPs) based on an ultraviolet continuously variable spatial frequency photolithography process has been proposed. The process aims to provide low cost fabrication of variable spatial frequency grating pixels with high efficiency. We fabricate 2 inch backlight plate with nine viewing directions, and the pitch of each diffractive pixel varies between 441 nm and 578 nm. The properties of SMGPs are investigated by the measurement of diffraction efficiency dependence on viewing angle under a collimated 650 nm LED light source at an incidence angle of 60°. The variation of diffraction efficiency with regards to viewing angle is weak. The measured diffraction efficiency is around 6%, which is in good agreement with the simulated value.

This work has demonstrated that with silver superlens, the resolution of conventional optical lithography can be improved significantly. Experimental and simulative results are given to verify the facts that the resolution and the pattern fidelity are sensitive to the contact tightness between layers.

A soft lithographic approach using a modified polyurethane acrylate (PUA) mold for the fabrication of sub-wavelength antireflective structure on polymer film is reported. By introducing an intermediate transferring PUA mold generated by an anodized aluminum oxide membrane, there is no need either to heat nor to deposit metal as a seed layer. Therefore, the most costly and time-consuming master preparation step in the conventional process chain is not a necessity. The soft PUA mold provides a high resolution of 100 nm with an aspect ratio of 1.7 and a conformal contact with the substrate and reduces the pressure needed during the imprinting steps. It is numerically verified that the antireflective film with nanopores has a similar fascinating broadband antireflective effect compared with that of its complementary nanonipple one. In our experiment, the average transmission efficiency of the PET film with dual-side nanopores can be enhanced to 98.7% at normal incidence and 92.5% at an incident angle of 60° over a range of 400~800 nm of the spectrum. The proposed method is simple and cost-effective and the fabricated antireflective polymer film can be mounted on the surfaces of various optical devices for the reduction of Fresnel reflections.

Organic-based optoelectronic devices, including light-emitting diodes (OLEDs) and solar cells (OSCs) hold great promise as low-cost and large-area electro-optical devices and renewable energy sources. However, further improvement in efficiency remains a daunting challenge due to limited light extraction or absorption in conventional device architectures. Here we report a universal method of optical manipulation of light by integrating a dual-side bio-inspired moth's eye nanostructure with broadband anti-reflective and quasi-omnidirectional properties. Light out-coupling efficiency of OLEDs with stacked triple emission units is over 2 times that of a conventional device, resulting in drastic increase in external quantum efficiency and current efficiency to 119.7% and 366 cd A(-1) without introducing spectral distortion and directionality. Similarly, the light in-coupling efficiency of OSCs is increased 20%, yielding an enhanced power conversion efficiency of 9.33%. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency organic optoelectronic designs.

An embedded Ag mesh transparent conductive electrode (TCE) on flexible substrate, which is suitable for polymer dispersed liquid crystal (PDLC) device, is demonstrated. With the combination of soft ultra-violet nanoimprinting lithography and scrape technique, it offers parallel processing with high resolution (10000dpi), as well as remarkable simplicity and fully controllable flexibility to tailor the transmittance and sheet resistance. While being able to achieve maximum transmittance 60% in the on state and the minimum 0.1% in the off state, the PDLC smart window displays low sheet resistance (5.58 Ω/sq.) under low driven voltage (30V) safe for human. The main advantage of adoption of PDLC as an optically scattering element lies in the fact that there needs no mechanical part for in situ tunability. An enhancement factor of 50 of the diffraction intensity is observed experimentally. The embedded Ag mesh TCE for PDLC device has an environmentally-friendly additive manufacturing process inherently. Compared to existing solutions, the fabricated sample shows superior performance in both optoelectronic and mechanic characteristics. We envision that the embedded Ag mesh TCE will enable economically widen application of PDLC devices on flexible substrate.

A cost-effective method, using reactive ion etch (RIE) process to etch Si with Ag nanoparticle mask for fabricating antireflection structure, is proposed. The formation of Ag nanoparticle adopts wet-chemical method to deposit Ag layer on Si substrate, and then through rapid thermal annealing of Ag at 200°C-600°Crange, Ag nanoparticle were formed on Si substrate. Effects of parameters including etching parameters and deposited factors were investigated. According to analysis result of experiment, a group of high performance antireflection structure parameters was obtained.

Microlens arrays film fabricated by UV roll-to-roll nanoimprinting lithography is introduced on glass substrate to improve the out-coupling efficiency of organic light-emitting devices. The microlenses suppress wave guiding loss in the substrate and a theoretical model, based on Monto-Carlo model, is developed to simulate the enhancement effects. The numerical results show that ellipsoidal-like microlens array can increase the efficiency by a factor of more than 35% and the luminance density distribution along the orthogonal directions can be compressed by 10 degree. Such a microlens array mold is fabricated by a combination of DMD-based laser direct writing lithography and thermal reflow method, followed by electroforming for transferring the surface structure to a nickel plate. The obtained mold is wrapped on a roller for the mass production of microlens array film by UV roll-to-roll nanoimprinting process. OLED attached with such microlens array film with a maximum increase of 35% in efficiency is achieved and directional out-coupling phenomenon can be observed experimentally. Such a directional out-coupling microlens array film can be used to OLED to enhance the luminous intensity efficiency and save power consumption for future lighting and display application.

A reflective-type color filter in the visible range is theoretically investigated. It consists of a transparent flexible substrate, a layer of thick metal, and two-dimensional dielectric-metal grating. The filter proposed here has the advangtages of insensitivity to incident-angle and polarization-independence. It is found that the variations of its geometric parameters can tune the selective wavelength to generate different colors. The angular dependence of the reflection spectrum for TM and TE polarized light is simulated and analyzed. The position of the reflection valley and the full-width at half-maximum (FWHM) remain almost unchanged when the incident angle is increased to 30 degree. The useful future of the structure is the low dependence of the reflection spectrum on the incident-angle and the polarizations which can be utilized for reflective display.

We experimentally demonstrate that at terahertz frequencies perfect plasmonic absorbers made on a highly doped silicon platform can be easily realized, exhibiting near-zero dips in the reflection spectra. The unit cell of the absorber consists of a dielectric layer of SiO2 film sandwiched between a highly doped silicon wafer and the copper structures, in the form of either one-dimensional stripe array or two-dimensional cross array. The reflection spectrum of the proposed absorbers are characterized using a terahertz time-domain spectroscopy system and the experimental results are in good agreement with numerical simulations. The dependence of the absorption on the THz polarization for both the 1D and 2D absorbers are also investigated. The high performance together with the easy fabrication processes presented in this paper show that the plasmonic absorber holds high prospect in terahertz applications.

We report the fabrication and characterization of second-order external distributed feedback (DFB) lasers based on blue-emitting polymer poly (9, 9-dioctyl-fluorene) (PFO). The relief grating prepared in the photo-resist layer on top of the gain medium was directly employed as the resonator. The effect of various structural parameters including the thickness of the active film, the thickness of the residue layer, and the depth of the relief grating on performance of these polymer lasers was investigated. An analytical approach based on the slab waveguiding theory and the Bragg condition was developed to accurately determine the lasing wavelength. We found that laser threshold increases monotonously as the thickness of the residue layer increases. The presence of the residue layer between the relief grating and the organic semiconductor layer weakens the strength of light coupling between the two layers, leading to a decreased gain for the specific lasing mode. The lowest laser threshold level of 80 μJ cm−2 was obtained when the thickness of the gain medium was around 250 nm, indicating an optimum balance between light feedback provided by the grating and optical amplification in the organic semiconductor. Our results not only provide insights into working mechanisms of external DFB polymer lasers, but also design rules for fabricating them.

Advanced light manipulation is extremely attractive for applications in organic optoelectronics to enhance light harvesting efficiency. A novel method of fabricating high-efficiency organic solar cells (OSCs) is proposed using biomimetic moth eye nanostructures in a quasi-periodic gradient shape active layer and an antireflective coating. A 24.3% increase in photocurrent is realized without sacrificing dark electrical properties, yielding a 22.2% enhancement in power conversion efficiency to a record of 7.86% for OSCs with a poly(3-hexylthiophene-2,5-diyl):indene-C60 bis-adduct (P3HT:ICBA) active layer. The experimental and theoretical characterizations verify that the substantial improvement of OSCs is mainly ascribed to the self-enhanced absorption resulting from the broadband polarization-insensitive light trapping in biomimetic nanostructured active layer, the reduction in reflectance by the antireflective coating, and surface plasmonic effect excited by corrugated metallic electrode. It is noteworthy that the pathway described here is promising for opening up opportunities to realize high-performance OSCs towards the future photovoltaic applications.

A type of tunable liquid crystal diffractive lens (TLCDL) for monochromatic wave base on multiorder diffraction is proposed and demonstrated. Two TLCDLs were designed using patterned indium tin oxide and a conductive surface relief electrode, respectively. The focus tuning mechanism of the lens has been proved using multiorder diffractive structure. One TLCDL with three switchable focal lengths was fabricated using an imprinting technique, which significantly reduced fabrication complexity. Electro-optic performances of the TLCDL were studied with monochromatic illumination. High image quality with low operating voltage and fast response time has been realized.

Microlens arrays film fabricated by ultra-violet (UV) roll-to-roll nanoimprinting lithography is introduced on glass substrate to directionally coupling the efficiency of organic light-emitting devices (OLEDs). The microlenses suppress wave guiding loss in the substrate and a theoretical model, based on Monte-Carlo model, is developed to simulate the enhancement effects. The numerical results show that ellipsoidal-like microlens array can not only increase the efficiency by a factor of more than 35%, but also directionally couple output light with the luminance density distribution along the orthogonal directions compressed by 10 degrees. Such a microlens array mould is fabricated by a combination of DMD-based laser direct writing lithography and thermal reflow method, followed by electroforming for transferring the surface structure to a nickel plate. The obtained mould is wrapped on a roller for the mass production of microlens array film by UV roll-to-roll nanoimprinting process. OLED attached with such microlens array film with a maximum increase of 35% in efficiency is achieved and directional out-coupling phenomenon can be observed experimentally. Such a directional out-coupling microlens array film can be used in OLED to enhance the luminous intensity efficiency and save power consumption for future lighting and display application.

We propose and demonstrate a tunable-focus liquid crystal Fresnel zone lens (TLCFZL) based on harmonic diffraction. The physical mechanism of the focus tuning is based on a multi-order diffraction process using a shallow surface relief type harmonic diffractive structure with uniform electrodes which results in significantly reduced fabrication complexity and excellent electro-optic performances. A rapid fabrication process including imprinting technique is studied, from which a high performance TLCFZL with three switchable focus lengths and high diffraction efficiency (about 70%) is fabricated. Focusing and imaging properties of the TFLCFZL are tested. The highest resolution of the lens reaches 22.6 lp/mm with low operating voltage of less than 7.2 Vrm and response time of ∼200 ms.

Light out-coupling efficiency of organic light-emitting devices from high-index glass substrate into air is enhanced by attaching ordered microlens arrays, which are fabricated by a roll-to-roll mold transfer process. The dependence of microlens geometries on light extraction is analyzed experimentally and theoretically. An increase of 60% in the light out-coupling with an optimized elliptical microlens array is achieved over a conventional device without affecting the electroluminescent spectrum.