Flexible transparent films that have excellent photoelectric properties, mechanical and thermal stability, and antibacterial properties, are highly desirable for applications in flexible and wearable electronics. Multifunctional transparent conductive films (TCFs) with long silver nanowires (AgNWs, average length = 80 μm and average diameter = 88 nm)/transparent polyimide (PI) structures which were fabricated by using a facile, scalable, environmentally-friendly, and full-solution process, can satisfy all the requirements above. The AgNW/PI composite films show excellent opto-electrical properties (e.g., 7.5 ohm sq−1, at 81.1% transmittance) and mechanical flexibility across a wide temperature range, from room temperature to 300 °C. The AgNW networks were embedded into the transparent PI film surface, which could decrease the surface roughness (Rrms < 2.0 nm), and enhance the composite films' resistance to peeling, fracture, and oxidation, which expands the range of TCF applications considerably. Additionally, in exploring promising applications, the function of the transparent heater and the antibacterial properties of the composite films were also studied. These characteristics make the composite films excellent candidates for substrates for flexible and wearable electronic devices.

In this work, the performance of p–i–n hydrogenated amorphous silicon thin film solar cells by adopting n-type silicon carbide (n-SiCx:H) layer was investigated. By varying CH4/SiH4 gas flow ratio, refractive index and electrical conductivity of n-SiCx:H thin films were changed in the range of 3.4 to 3.8 and 1.48E−5 to 1.24 S/cm, respectively. Compared with solar cells with n-Si:H/Ag configuration, short-circuit current density (Jsc) of solar cells with n-SiCx:H/Ag configuration was improved up to 8.4%, which was comparable with that of solar cells with n-Si:H/ZnO/Ag configuration. Improved Jsc was related with enhanced spectral response at long wavelength of 500–800 nm. It was supposed that the decreased refractive index of n-SiCx:H layer resulted in the increased back reflectance, which contributed to the improved Jsc. Our experiments demonstrated that n-SiCx:H thin films were attractive choice because they functioned both as n-layer and interlayer in back reflector, and their deposition method was compatible with preparation process of solar cells.

•Optoelectronic properties of thin film almost unchanged by 0.2 wt% TiO2co-doping•Damp heat stability was improved by 0.2 wt% TiO2co-doping.•Weak-acid resistance was improved by 0.2 wt% TiO2co-doping.In this work, we proposed a strategy to improve the damp-heat stability and weak-acid resistance of gallium doped zinc oxide (GZO) thin films by co-doping TiO2 into GZO targets. Results showed that GZO thin films with a 0.2 wt% TiO2 co-doping in the target (GTZO) exhibited a resistivity of 5.1 × 10− 4 Ω·cm and an average transmittance of 82.9%. The relative change in sheet resistance was as low as 5.1% after 24 h damp heat treatment in conditions of 97% relative humidity at 121 °C. A craterlike textured surface with a high haze value was not found in GTZO thin films after dipping in 1 vol% HCl solution for 10 min. These results showed that GTZO thin films have great potential for use as transparent electrode in extreme outdoor conditions.

The flexible transparent conductive films (FTCFs) of silver nanowire-polyethylene terephthalate (AgNW-PET) were prepared by a facile method including vacuum filtration and mold transferring. The effect of silver nanowire weight density on the optical and electrical properties of films, as well as the electrical percolation was investigated. The obtained typical AgNW-PET film exhibited high figure of merit of 31.3 × 10−3 Ω−1 with low sheet resistance of 4.95 Ω sq−1 and high transparency at 550 nm of 83.0% (excluding PET substrate). The resulting FTCFs based on PET substrate with high transmittance and low sheet resistance have a great potential in the application of high-performance flexible electronics and photovoltaic devices.

•Carrier concentration was mainly tailored by target Ga2O3 concentration.•The values of plasmonic resonances wavelength are changed from 1.35 to 2.39 μm.•The permittivity of film grown at 5 wt% Ga2O3 concentration is negative at 1.55 μm.•Change of absorption loss and carrier concentration shows the opposite tendency.•The carrier density determines that the film reaches the ideal plasmonic metamaterial.In this paper, Ga-doped ZnO (GZO) thin films are deposited on glass substrates by radio frequency magnetron sputtering for low loss plasmonic applications. The effects of Ga2O3 content in the target and substrate temperature on the electrical, structural and optical properties of GZO films are investigated. Film with the highest carrier concentration of 7.0 × 1020 cm− 3 was obtained at a Ga2O3 content of 5 wt% in the target under room temperature deposition. With increasing deposition temperature, the lowest electrical resistivity of 3.8 × 10− 4 Ω cm was acquired at a deposition temperature of 200 °C. The values of plasmonic resonances wavelength could be changed from 1.35 to 2.39 μm by adjusting the carrier concentration. Material absorption losses in these GZO films are 10 times lower than that of conventional Ag films at telecommunication wavelengths. These results make GZO a promising low-loss plasmonic material operating at telecommunication wavelengths.

Flexible transparent conductive films (TCFs) are used in a variety of optoelectronic devices. However, their use is limited due to poor thermostability. We report hybrid TCFs incorporation in both aluminum-doped zinc oxide (AZO) and silver nanowires (AgNWs). The layered AZO/AgNWs/AZO structure was deposited onto a transparent polyimide (PI) substrate and displayed excellent thermostability. When heated to 250 °C for 1 h, the change in resistivity (Rc) was less than 10% (Rc of pure AgNW film > 500) while retaining good photoelectric properties (Rsh = 8.6 Ohm/sq and T = 74.4%). Layering the AgNW network between AZO films decreased the surface roughness (Rrms < 8 nm) and enhances the mechanical flexibility of the hybrid films. The combination of these characteristics makes the hybrid film an excellent candidate for substrates of novel flexible optoelectronic devices which require high-temperature processing.Keywords: mechanical flexibility; thermal stability; transparent conductive films; transparent polyimide substrate

•Double-layered AR coatings were prepared using hybridized HSN sols.•One- and two-sided AR coated superstrates were implemented in tandem solar cells.•Sunlight distribution and trapping were simultaneous realized via the AR coatings.•The two-sided AR coatings demonstrated the largest increases in current densities.•The multiscale textured BZO originated from the unique morphology of HSN.Implementing antireflection (AR) coatings in micromorph tandem solar cells is a challenging process in which not only more sunlight should get conducted into the cells, but also the current matching between subcells should either be maintained or get improved. In this work, the novel double-layered AR coatings were prepared on either one side or two sides of glass superstrates using hybridized hollow silica nanosphere (HSN) sols. As a result of improvement in light distribution via double-layered AR coatings, the current difference between the top and bottom subcells was decreased to be 0.05 mA/cm2, much smaller than that of untreated cells, 0.33 mA/cm2. Furthermore, the cells grown on the two-sided AR coated superstrates demonstrated the largest increases in current densities of top and bottom subcells, 4.20% and 7.53%, respectively, which were much higher than those of the cells on one-sided AR coated superstrates. The underlying origin was ascribed to the better light trapping induced by multiscale texturing at front boron-doped zinc oxide (BZO) electrodes, which resulted from the conformal growth of BZO on HSNs with unique surface morphologies. The findings provided a practical way to simultaneously realize light distribution and trapping using the two-sided AR coated glass superstrates without any amendment of layers inside micromorph tandem solar cells.

•A facile process is established to prepare the nano-imprinting master.•The master exhibits combined micron- and nano-scale featured surface.•The master exhibits an averaged haze value of 54.1% from 380 to 1100 nm.•A maximum summed current enhancement of 35.5% was obtained.•The efficiency of the tandem cell was improved from 8% to 10.0 ± 0.3%.This paper reports a facile method to prepare a textured surface with combined micron- and nano-scale surface features, which is used as master for nano-imprinting process to obtain transparent front electrodes in thin-film silicon tandem cells. The micron- and nano-scale surface features of the master are formed by combination of SiO2 sphere pre-deposition and ZnO textured growth. The master exhibits an averaged total transmittance value of 89.7% and an averaged haze value of 54.1% for the wavelength from 380 to 1100 nm. Comparing to the flat reference cell, the thin-film Si tandem cell deposited on the superstrate prepared using this master shows substantial decrease in reflectance at long wavelengths and drastic gain in the photocurrent of the bottom cell, the maximum summed current is enhanced by 35.5%, and the convert efficiency is improved from 8% to 10.0 ± 0.3%.

Highly flexible and transparent film heaters (TFHs) with superior mechanical and thermal stability were fabricated by embedding silver nanowires (AgNWs) into transparent polyimide (PI) films using a solution coating method. The fabricated AgNW/PI hybrid TFHs exhibited higher heating temperatures (∼96 °C) with lower input voltage (∼6 V), shorter response time (T < 40 s), and lower power consumption (160.6 °C cm2 W−1) than ITO/FTO heaters, as well as stability after repeated use. The AgNW/PI hybrid TFHs also showed excellent resistance to bending. After undergoing outer bending for a 1000 times, the change of sheet resistance was less than 18%. The effective embedment of the AgNW network in the surface of the transparent PI film not only decreased the surface roughness (Rrms < 1 nm) but also enhanced the resistance against oxidation and moisture. Potential applications of the AgNW/PI TFHs in window defogging and thermochromics are demonstrated.

Morphology-controllable Cu2SnS3 thin films on Mo-glass were prepared via a facile in situ one-step solvothermal process and used in dye-sensitized solar cells as counter electrodes. The effects of different solvents on the morphology of films were investigated. DSC based on the porous net-like Cu2SnS3 thin film as counter electrodes showed a power conversion efficiency of 2.30%, which was improved to 3.35% after annealing.

In order to investigate the effects of bending strain on electric-magnetic coupling, we fabricated and characterized two types of flexible terahertz (THz) metamaterials on polyethylene naphthalate (PEN) substrates, which had either asymmetric or symmetric configuration. The asymmetric flexible THz metamaterials showed a plasmon-induced transparency originating from electric-magnetic coupling. The transparency was rather robust and insensitive to strain. The symmetric metamaterials demonstrated a transmission dip at a frequency of 1.35 THz without applied strain due to electric resonance. However, if strain gradually varied, a continuously tunable transmission dip was observed at a frequency of 1.1 THz, which could be ascribed to electric-magnetic coupling induced by symmetry breaking. The promising results suggested that the asymmetric and the symmetric flexible THz metamaterials could find potential applications in curved devices and remote stress sensors, respectively.

Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (∼8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the resistivity of the printed silver patterns decreased to 3.7 μΩ cm, which is close to twice that of bulk silver. Various factors affecting the resistivity of the printed silver patterns, such as annealing temperature and the number of printing cycles, were investigated. The resulting high conductivity of the printed silver patterns reached over 20% of the bulk silver value under ambient conditions, which enabled the fabrication of flexible electronic devices, as demonstrated by the inkjet printing of conductive circuits of LED devices.

Hybrid transparent conductive films (TCFs) with a sandwich structure composed of aluminum-doped zinc oxide (AZO) and Ag nanowires (AgNWs) were deposited on polyethylene terephthalate (PET) substrates. The AZO layers were prepared at room temperature by RF magnetron sputtering. The AgNWs were synthesized by a modified polyol method and inserted into the AZO layers. The optical properties and conductivity can be modified by the number of spin-coating cycles of an AgNWs suspension. Typically, an AZO/AgNW/AZO hybrid film exhibited an optical transmittance of 80.5%, a sheet resistance of 27.6 Ω sq−1 and an optical haze of 14.9%. The increase in optical haze caused by the silver nanowires may be beneficial for applications in solar cells. The hybrid films presented excellent flexible stability, showing only minor resistance changes and no surface cracks compared with pure AZO films. The AZO layers acted as the protecting layers that enhanced the adhesive and thermal stability of the hybrid films. The resulting hybrid TCFs with an AZO/AgNW/AZO sandwich structure show potential applications in flexible electronics, energy storage and photovoltaic devices.

Antireflection (AR) coatings that exhibit multifunctional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging properties, were developed based on hollow silica–silica nanocomposites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol–gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86–97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.Keywords: antifogging; antireflection coatings; durability; hollow silica; multifunctional; nanocomposites;

•Silver nanoparticle-based ink has been synthesised for directly printing silver films on paper substrates with inkjet printer.•Silver films can be sintered at room temperature by printing poly(diallyldimethylammonium chloride) solution.•The mechanism of room temperature sintering was proposed based on the electrical and the morphological properties of silver films.Water-dispersible Ag nanoparticles (NPs) were synthesised with polyacrylic acid as capping agents and prepared as an Ag NP-based ink. An approach to achieve coalescence and sintering of Ag NPs at room temperature was presented. After inkjet printing Ag NP-based ink on paper substrates, the Ag NPs underwent spontaneous coalescence when they came into contact with a poly(diallyldimethylammonium chloride) (PDAC) solution even without a traditional sintering process. This phenomenon rapidly decreased the sheet resistance of the films. The room-temperature sintering mechanism was then proposed based on the electrical and the morphological properties of Ag films with and without PDAC solutions.

•An ink from silver nanoparticles coated with polyacrylic acid was prepared.•The ink was used for inkjet-printed tracks at varying printing parameters.•The conductivity of printed tracks sintered at 150 °C increased to 2.1 × 107 S/m.•Mechanism for dispersion and aggregation of the nanoparticles in ink is discussed.Silver nanoparticles with a mean diameter of approximately 30 nm were synthesized by reduction of silver nitrate with triethanolamine in the presence of polyacrylic acid. Silver nanoparticle-based ink was prepared by dispersing silver nanoparticles into a mixture of water and ethylene glycol. The mechanism for the dispersion and aggregation of silver nanoparticles in ink is discussed. The strong electrostatic repulsions of the carboxylate anions of the adsorbed polyacrylic acid molecules disturbed the aggregation of metal particles in solutions with a high pH value (pH > 5). An inkjet printer was used to deposit this silver nanoparticle-based ink to form silver patterns on photo paper. The actual printing qualities of the silver tracks were then analyzed by variation of printing passes, sintering temperature and time. The results showed that sintering temperature and time are associated strongly with the conductivity of the inkjet-printed conductive patterns. The conductivity of printed patterns sintered at 150 °C increased to 2.1 × 107 S m−1, which was approximately one third that of bulk silver. In addition, silver tracks on paper substrate also showed better electrical performance after folding. This study demonstrated that the resulting ink-jet printed patterns can be used as conductive tracks in flexible electronic devices.

In this work, heavily doped ZnO thin films with carrier concentrations of 1.7 × 1020–1.1 × 1021 cm−3 were prepared on glass substrates using direct current magnetron sputtering combined with rapid thermal annealing (RTA). The effects of RTA on the electrical transport properties of the thin films were investigated. Results showed that the resistivities of the thin films deposited at low temperatures were markedly improved due to the increased mobilities and/or carrier concentrations. Temperature-dependent Hall measurements and theoretical calculations suggested that the influence of grain boundary scattering was negligible for all the samples and the mobility was mainly determined by ionized impurity scattering. The influence of crystallographic defects on the mobility could be effectively reduced via RTA when the carrier concentration was above 4.0 × 1020 cm−3, resulting in a mobility and resistivity close to the ionized impurity scattering theoretical estimation. The highest mobility of 46 cm2 V−1 s−1 at the resistivity of 2.8 × 10−4 Ω cm and the lowest resistivity of 2.6 × 10−4 Ω cm were achieved for the RTA-treated 1 wt.% Al-doped ZnO and 5 wt.% Ga-doped ZnO thin films, respectively.

This paper reports a facile means to gradually tailor refractive index from an ultra-low-n of 1.10–1.45 based on hollow silica nanospheres hybridized with acid-catalyzed silica. The influences of the hybridization on refractive index, thin-film uniformity, and roughness were systematically investigated. The single-layered antireflection (AR) coatings and the three-layered AR coatings were prepared using the hybridized thin films as building blocks. The former showed the near-perfect transmittance and reflectance, 99.16 and 0.42 %, respectively, at a single wavelength of 600 nm, while the average transmittance (Tave) and reflectance (Rave) from the near ultraviolet (UV) to the visible region (300–800 nm) were moderate; the latter demonstrated an excellent AR capability in broadband that Tave reaches 97.29 %, much higher than that of the single-layered AR coating, 95.86 %. More interestingly, the three-layered AR coating showed an average transmittance of 97.94 % in the near-UV wavelength range from 345 to 400 nm and it was 6.77 % higher than that of bare glass. Moreover, the three-layered AR coatings had the less degradation in transmission and surface morphology after the highly-accelerated temperature and humidity stress tests, and the wet abrasion scrub tests. The findings imply that both good optical performance and durability are likely to be achieved using the sol–gel derived multilayered AR coatings.

This paper reports the use of a combination of numerical calculations and experimental work to establish the optimum photovoltaic transmittance (Tpv) and durability of the quarter wave, the quarter-half wave, and the non-quarter wave double-layer TiO2–SiO2 and ZrO2–SiO2 antireflective coatings (ARCs) on solar glass towards practical photovoltaic applications. Numerical calculations based on 4 × 4 propagation matrix method indicated that the non-quarter wave double-layer ARCs exhibited higher Tpv values than those of the quarter wave and the quarter-half wave ARCs. Such calculated values are in good agreement with the experimental Tpv values. For examples, the Tpv values for the non-quarter wave double-layer TiO2–SiO2 and ZrO2–SiO2 ARCs prepared by sol–gel reached 94.4 ± 0.1% and 94.3 ± 0.1%, respectively. In terms of the coating durability, the non-quarter wave double-layer coatings with a dense and thicker TiO2 or ZrO2 barrier layer on solar glass exhibited less than 1% reduction in Tpv after 96 h highly-accelerated temperature and humidity stress test (HAST), as compared with the standard single-layer porous SiO2 used in industry which tested in the same HAST conditions to be greater than (15.4%) after 48 h. Single crystalline Si modules encapsulated by the non-quarter wave TiO2–SiO2 or ZrO2–SiO2 AR-coated glass are more durable, with only less than 10% degradation in efficiency after 48 h HAST, as compared with Si modules encapsulated by single-layer porous SiO2 AR-coated glass which have signification loss in efficiency (circa. 21.8%).Highlights► The non-quarter wave double-layer ARCs demonstrated the highest Tpv. ► The highest Tpv of the ARCs showed an increase more than 3% over the solar glass. ► The durability strongly depended on the thickness of the TiO2 or the ZrO2 layer. ► The Tpv degradation for thicker ARCs was less than 1% after 96 h HAST. ► The solar cells with ARCs demonstrated a smaller efficiency degradation.

Phosphorus (P)-doped silicon nanocrystals (Si-NCs) embedded in SiC matrix were prepared using magnetron sputtering and rapid thermal annealing with heavily P-doped Czochralski silicon as the doping target. The microstructure and electrical properties of the Si-NC thin films were characterized using transmission electron microscope, Raman spectroscopy and Hall measurement. It was observed that the microstructure changed from geometrically isolated Si-NCs to network Si-NCs with the annealing temperatures from 800 to 1200 °C. The evolution of microstructure led to the significant change of conductivity (10−6 - 101 S cm−1) in the Si0.85C0.15 thin films that possessing a fixed phosphorus concentration. A percolation threshold of crystalline-silicon (c-Si) content (30–40%) was found for the considerable increase of conductivity, where the carrier concentration dominated it. It suggested that the network Si-NCs not only increased the carrier mobility, but also boosted the carrier concentration. In addition, for the Si0.85C0.15 thin film with c-Si content above percolation threshold, the activate energy of conductivity could be lower than 70 meV and the work function lower than 4.10 eV.

In this work, several Al-doped ZnO thin films were sequentially deposited from a high temperature sintered sputtering target in order to understand the effect of ZnAl2O4 segregation in target on optical and electrical properties of the deposited films. It was observed that the Al-doped ZnO films were all well (002) oriented with increasing 2θ from 34.25 to 34.38°, which corresponded to the lattice shrinkage from 5.232 Å to 5.212 Å. The corresponding band gaps for the Al-doped ZnO films increased from 3.47 eV to 3.54 eV as determined from transmittance spectra and the resistivity decreased from 3.7 × 10− 3 Ω cm to 1.3 × 10− 3 Ω cm. These changes were ascribed to the Al concentration increase from the polished surface to the inner target in the target due to surface segregation of ZnAl2O4 during the high temperature sintering process.Highlights► The aluminum doped zinc oxide thin films were sequentially deposited from a new high-temperature sintered ceramic target. ► These thin films revealed a continuous shrinkage of c-axial lattice constant, increase of band gap and conductivity. ► These changes were ascribed to the Al-deficiency at the target surface due to ZnAl2O4 segregation.

•SiC-matrix p-type Si-NCs were doped through the heavily B-doped CZ-Si target.•Conductivity increased by 10–100 times when Ts was 200 °C.•Crystalline fraction increased by ∼5%when Ts was 200 °C.•fcc Si-NCs formed in the surface layer when Ts was 200 °C.Boron (B)-doped silicon-rich SiC (SiCx, 0