High Visible Transmittance Research Articles

BaZrO3/MgO-templated epitaxy showing a conductivity increase of three orders of magnitude for the Ba0.95La0.05SnO3 films on Al2O3 substrates, with very high transparency and X-band electromagnetic shielding

Transparent conductors with electromagnetic shielding capabilities (TC-EMS) are rare, despite their significant potential for creating new functionalities in energy and military applications. Here, we investigate the potential of La-doped BaSnO3 (BLSO) for TC-EMS since its epitaxial film has been known to have low sheet resistance and high visible transmittance. However, films grown on industrially practical Al2O3 substrates exhibit a sheet resistance three orders of magnitude higher than that of reported films grown on perovskites. Here, this problem is addressed by templating a BaZrO3/MgO bilayer on (0001)-oriented Al2O3 substrates to yield single-crystalline BLSO epitaxial films. The absence of grain boundaries in the epitaxial films minimizes the electron scattering. Due to the affirmative correlation between the conductivity and crystallinity, 5% La doping is optimal among the 5−20% La concentrations studied; these 480-nm-thick films have the highest crystallinity and the lowest sheet resistances of ~28 Ω ▯−1; this value is similar to that of single-crystalline levels. Due to their very high transmittances (~82% in a range 400−1000 nm) and effective X-band electromagnetic shielding (~18.6 dB), the BLSO epitaxial films grown on Al2O3 have great potential to be used for inexpensive TC-EMS applications.

Semitransparent Perovskite Solar Cells with an Evaporated Ultra‐Thin Perovskite Absorber

AbstractMetal halide perovskites are of great interest for application in semitransparent solar cells due to their tunable bandgap and high performance. However, fabricating high‐efficiency perovskite semitransparent devices with high average visible transmittance (AVT) is challenging because of their high absorption coefficient. Here, a co‐evaporation process is adopted to fabricate ultra‐thin CsPbI3 perovskite films. The smooth surface and orientated crystal growth of the evaporated perovskite films make it possible to achieve 10 nm thin films with compact and continuous morphology without pinholes. When integrated into a p‐i‐n device structure of glass/ITO/PTAA/perovskite/PCBM/BCP/Al/Ag with an optimized transparent electrode, these ultra‐thin layers result in an impressive open‐circuit voltage (VOC) of 1.08 V and a fill factor (FF) of 80%. Consequently, a power conversion efficiency (PCE) of 3.6% with an AVT above 50% is demonstrated, which is the first report for a perovskite device of a 10 nm active layer thickness with high VOC, FF and AVT. These findings demonstrate that deposition by thermal evaporation makes it possible to form compact ultra‐thin perovskite films, which are of great interest for future smart windows, light‐emitting diodes, and tandem device applications.

La-doped BaSnO3 for electromagnetic shielding transparent conductors

In this work, we find that La-doped BaSnO3 (BLSO) is shown to be a promising electromagnetic shielding transparent conductor. While films grown on industrially practical optoelectronic MgAl2O4 substrates have higher sheet resistance by three orders of magnitude than in previous reports, we show how to recover the sheet resistance close to the single-crystal level by use of an MgO template layer which enables high quality (001)-oriented BLSO epitaxial film growth on (001) MgAl2O4. There is a positive correlation between crystallinity and conductivity; high crystallinity minimizes scattering of free electrons. By applying this design principle to 5–20% doped films, we find that highly crystalline 5% La-doped BLSO films exhibit low sheet resistance of ~ 8.7 Ω ▯ −1, high visible transmittance of ~ 80%, and high X-band electromagnetic shielding effectiveness of ~ 25.9 dB, thus outperforming transparent conducting oxides films of Sn-doped In2O3 and SrMoO3.Graphical

Breaking through the plasma wavelength barrier to extend the transparency range of ultrathin indium tin oxide films into the far infrared

Indium tin oxide (ITO) film, which is the most commonly used transparent conductive film (TCF), has traditionally been believed to be transparent in the visible spectrum but to reflect infrared (IR) light beyond the plasma wavelength (λp). However, our theoretical analysis challenges this notion by demonstrating that an ultrathin ITO TCF that is thinner than the light's penetration depth can overcome the transmission barrier at λp. To validate the theoretical modeling, we have successfully fabricated ultrathin ITO films that, despite having λp ≈ 1 μm, remain transparent from 400 nm to 20 μm. This represents the broadest transparency range ever reported for any In2O3-based TCF. The 10-nm-thick ITO TCFs have high visible transmittance (91.0% at 550 nm), low resistivity (5 × 10−4 Ω cm), and good IR transmittance (averaging 60% over 1.35–18.35 μm). Their IR transparency facilitates radiative cooling of the underlying circuitry. When an operational resistor is enclosed by commercial ITO TCFs that are 140 nm thick, its temperature increases. However, using 10-nm-thick ITO TCFs instead of the commercial ones can completely avoid this temperature rise. Moreover, attaching a silver grid to a 10-nm-thick ITO TCF can reduce the effective sheet resistance to ∼10 Ω/□ at the expense of only ∼3% transmittance. This development paves the way for large-scale applications that require low sheet resistance and far-IR transparency.

Solution Processed Semi-Transparent Organic Solar Cells Over 50% Visible Transmittance Enabled by Silver Nanowire Electrode with Sandwich Structure.

Photovoltaic windows with easy installation for the power supply of household appliances have long been a desire of energy researchers. However, due to the lack of top electrodes that offer both high transparency and low sheet resistance, the development of high-transparency photovoltaic windows for indoor lighting scenarios has lagged significantly behind photovoltaic windows where privacy issues are involved. Addressing this issue, this work develops a solution-processable transparent top electrode using sandwich structure silver nanowires, realizing high transparency in semi-transparent organic solar cells. The wettability and conducting properties of the electrode are improved by a modified hole-transport layer named HP. The semi-transparent solar cell exhibits good see-through properties at a high average visible transmittance of 50.8%, with power conversion efficiency of 7.34%, and light utilization efficiency of 3.73%, which is the highest without optical modulations. Moreover, flexible devices based on the above-mentioned architecture also show excellent mechanical tolerance compared with Ag electrode counterparts, which retains 94.5% of their original efficiency after 1500 bending cycles. This work provides a valuable approach for fabricating solution-processed high transparency organic solar cells, which is essential in future applications in building integrated photovoltaics.

One-step assembly of organic-inorganic hybrid coatings with superior thermal insulation, sustainable antifogging and self-cleaning capabilities

Multifunctional transparent glass integrating energy-saving and antifogging properties has receiving continuous attention in basic research and practical applications, which is still plagued by the lack of simple and general methods for low-cost and large-area fabrication. Herein, a multifunctional window with high thermal insulation, antifogging, and self-cleaning functions is rationally fabricated via coating a mixture of polyacrylic acid (PAA), polypropylene glycol (PPG), 3-glycidyloxypropyltrimethoxysilane (KH-560), and cesium tungsten bronze (CWO) nanoparticles on a monolayer film. The synergistic effect between the plentiful hydroxyl/carboxyl groups of PAA/PPG and the nano-textured surface induced by CWO nanoparticles enabled the monolayer film to exhibit superhydrophilic, self-cleaning and antifogging capabilities. The film maintains its antifogging properties even after 80 rubbings of dust-free cloth and 120 days of exposure tests at room temperature. Moreover, the as-prepared window can reduce the indoor temperature by 15.8 °C compared to a normal window at noon. The energy simulation results demonstrate that such windows can reduce energy consumption by 18.9 % in local cities compared to traditional windows. The high visible light transmittance, low haze, stable and durable antifogging ability, distinguished energy-saving effect and climate adaptability, as well as the solution-based process of this multifunctional window make it promising for architectural and automotive glass applications.

Molecular design of cost-effective donor polymers with high visible transmission for eco-friendly and efficient semitransparent organic solar cells

Photoactive layer materials that overcome the trade-off between power conversion efficiency (PCE) and average visible transmittance (AVT) are required to prepare successful high-performance semitransparent organic solar cells (ST-OSCs). Among 12 novel cost-effective D–π=A polymers with high visible light transmission, P(3IN = 0.3)(3IN2F = 0.5)(BDD = 0.2) achieved a PCE of 14.0% and high stability in an eco-friendly solvent-processed OSC with BTP-eC9. This blend film exhibited an AVT of 62.1% and a color rendering index of 95.0, demonstrating the high potential for ST-OSCs. The ternary OSC with PM6 greatly enhances the PCE to 17.3%. Binary and ternary ST-OSCs achieve light utilization efficiencies (LUEs) of 4.38% and 4.04%, respectively, demonstrating the potential of the D–π=A structure. Under a 3000 K light-emitting diode light at 958 lx low illuminance, PCEs of 12.4% and 15.7% are obtained for binary and ternary ST-OSCs, respectively, and the indoor LUEs (LUIEs) of ST-OSCs are greatly enhanced to 5.52% and 5.48%, respectively. Air-processed eco-friendly ternary ST-OSC module (4.7 cm2) achieves not only a PCE of 12.1% and LUIE of 3.90% under 958 lx, but also color coordinates of (0.290, 0.323) and an infrared radiation rejection rate of 87.5%, meeting the civil engineering specifications for windows. This ST-OSC module can be a substitute power source of the thermo-hygrometer in real time, even operate at 195 lx, which paved the way towards zero-energy indoor and outdoor electrical devices as well as windows for buildings and vehicles.

Plasmonic aerogel window with structural coloration for energy-efficient and sustainable building envelopes

Renowned for superior thermal insulation properties, silica aerogel holds substantial promise for eco-friendly building construction. This study presents a novel colored transparent aerogel (CTA) window design that simultaneously achieves good light transmission, thermal insulation, and color modulation, which has not been reported before. The radiative properties of the core–shell plasmonic particle-doped aerogel were theoretically predicted by the combination of Mie theory and Monte Carlo methods. The results showed that the CTA window has high visible light transmittance (∼ 45%) and low thermal conductivity (∼ 0.018 W/m K), all while displaying an array of vivid colors. An energy consumption simulation of CTA windows in various climates in China showed potential energy savings of up to 90% compared to the single tinted window in severe cold regions. Moreover, a cost assessment of CTA windows is conducted to evaluate their economic feasibility and environmental benefits. This study introduces an innovative avenue to meet the escalating demand for both visually pleasing and energy-efficient materials, contributing profound insights into the realm of sustainable architectural design.

Longitudinal Through-Hole Architecture for Efficient and Thickness-Insensitive Semitransparent Organic Solar Cells.

Semi-transparent organic solar cells (ST-OSCs) have great potential for application in vehicle- or building-integrated solar energy harvesting. Ultrathin active layers and electrodes are typically utilized to guarantee high power conversion efficiency (PCE) and high average visible transmittance (AVT)simultaneously; however, such ultrathin parts are unsuitable for industrial high-throughput manufacturing. In this study, ST-OSCs are fabricated using a longitudinal through-hole architecture to achieve functional region division and to eliminate the dependence on ultrathin films. A complete circuit that vertically corresponds to the silver grid is responsible for obtaining high PCE, and the longitudinal through-holes embedded in it allow most of the light to pass through,where the overall transparency is associated with the through-hole specification rather than the thicknesses of active layer and electrode. Excellent photovoltaic performance over a wide range of transparency (9.80-60.03%), with PCEs ranging from 6.04% to 15.34% is achieved. More critically, this architecture allows printable 300-nm-thick devices to achieve a record-breaking light utilization efficiency (LUE) of 3.25%, and enables flexible ST-OSCs to exhibit better flexural endurance by dispersing the extrusion stress into the through-holes. This study paves the way for fabricating high-performance ST-OSCs and shows great promise for the commercialization of organic photovoltaics.

A general objective-orientated automatic optimization of multi-layer thermochromic smart glazes

VO2-based thermochromic smart glazes have attracted much attention for energy-saving buildings. Their practical applications need high visible luminous transmittance (Tlum) and high solar light modulation efficiency (ΔTsol). High Tlum and ΔTsol are difficult to be realized by a single-layer VO2 film, and constructing multi-layer film assemblies has been a widely adopted way to increase Tlum and ΔTsol. Tlum and ΔTsol of a multi-layer film assembly are multi-dimensional functions of the complex dielectric permittivity and the thickness of each layer, respectively. The current research reported a computer automatic searching of the total minimum of an evaluation function that together takes the cool-state Tlum, hot-state Tlum, and ΔTsol into account. It can be used to optimize a multi-layer assembly composed of any components according to the given objectives and weights for Tlum and ΔTsol. Different multi-layer film systems consisting of SiO2, TiO2, and VO2 layers were optimized. The best film system was proposed to be TiO2/VO2/TiO2/s, and the effects of objectives and weights on Tlum and ΔTsol were also checked. The physical reason that leads to high Tlum and ΔTsol was analyzed based on the optimized reflectance and transmittance spectra. The RGB tristimulus of the optimized multi-layer system can also be obtained from the transmittance spectra. The program can also realize an automatic optimization with some variables being constrained, and the composite layers are also involved under the basis of the Bruggeman effective media theory. The results showed that a satisfied objective-orientated optimization can be realized for a thermochromic layer system; this should be meaningful for the design and preparation of the multi-layer film assemblies according to the different user's demands.

Visible and infrared transparent conductive films with passive cooling capabilities

In order to facilitate radiative cooling in optoelectronic devices, it is necessary to employ infrared (IR) transparent conductive films (TCFs) that permit thermal radiation from internal circuits to pass through. This can be accomplished by using TCFs with a wide transparency range that extends into the far-IR spectrum. We have produced hafnium-doped indium oxide (InHfO) TCFs that have a wide transparency range spanning from 400 nm to 20 μm. These TCFs, with a thickness of 120 nm, exhibit a sheet resistance of approximately 200 Ω/□, high visible relative transmittance (90% at 550 nm, comparable to ITO), and IR transparency (66.9% in the 1.35–20 μm range). By replacing commercial ITO TCFs with InHfO TCFs, we successfully decreased the operating temperature of an enclosed resistor from 65.5 °C to 63.6 °C, and potentially to 61.1 °C via radiative cooling. This decrease corresponds to around 5–10% of the temperature difference between the resistor and room temperature. The InHfO TCFs we have prepared are suitable for a range of applications requiring transparency from the visible to the far-IR spectrum and may open up new avenues for optoelectronic applications.

Zinc oxide and indium tin oxide as embedding layers for ultrathin-silver-based transparent electrodes: A comparative study

The triple-layered structure comprising an ultrathin (∼10 nm) Ag layer embedded between two dielectric layers exhibits high visible light transmittance, electrical conductivity, and flexibility, and this triple-layered structure is thus considered as a promising candidate to replace the conventional single-layered indium tin oxide (ITO) transparent conductive electrodes in optoelectronic devices. While various dielectrics have been employed for the underlayer and overlayer, ITO and zinc oxide (ZnO) are the two common choices. In this study, we investigated the structural, electrical, optical, and thermal properties of triple-layered electrodes (dielectric underlayer/Ag/dielectric overlayer) comprising Ag, ZnO, and ITO; namely, ZnO/Ag/ZnO, ZnO/Ag/ITO, ITO/Ag/ITO, and ITO/Ag/ZnO electrodes, in which all layers were sputter-deposited at 293 K. The deposition of crystalline Ag onto crystalline ZnO and amorphous ITO surfaces exhibited distinctly dissimilar Ag nucleation dynamics, resulting in significant differences in the structural and thus electrical characteristics prior to Ag-layer-closure. After the formation of continuous Ag layers, the electrical conductivities became similar, whereas the optimized ITO/Ag/ZnO structure exhibited a considerably higher visible light transmittance than the other electrodes (with an average transmittance of 92.8%). Further, we found that the ZnO/Ag interface stability was significantly higher than that of the ITO/Ag interface during an electrically driven Joule heating process.

In-depth analysis on PTB7 based semi-transparent solar cell employing MoO3/Ag/WO3 contact for advanced optical performance and light utilization

Novel semi-transparent organic solar cells (ST-OSC) can be designed with high average visible transmittance (AVT) while at the same time exhibiting superior photovoltaic performance. This reach requires their design to be based not only on conventional window applications but also on functional industrial applications that require exceptional optical performance. In ST-OSC, high AVT can be achieved by photonic-based dielectric/metal/dielectric (DMD) transparent contact engineering. Functional optical modification can also be made with a fine-tuned design of DMD that includes a light management engineering-based approach. Thus, ST-OSCs can be suitable for aesthetic, colourful and decorative industrial windows that provide natural lighting. In this study, we determined optimal ST-OSCs based on a novel PTB7:PC71BM polymer blend with MoO3/Ag/WO3 asymmetric DMD top contact by examining extraordinary optical properties such as AVT, colour rendering index, correlated colour temperature and colour perception over 10 thousand designs. In addition to determining the optimality and extraordinary optical limits for PTB7, we also evaluated the photon-harvesting and photovoltaic performance of ST-OSCs from external quantum efficiency and quantum utilization efficiency. In optimal situations, ST-OSCs offering 48.75% AVT, 99.08 CRI, and sky-blue colours were designed and determined to generate short-circuit current densities of 9.88 mA·cm−2, 13.64 mA·cm−2, and 13.06 mA·cm−2, respectively.

Two-dimensional silver film for all-inorganic transparent photovoltaics

A transparent conductor with aluminum-doped zinc oxide (AZO)/Ag/Cu structure was developed and applied for extracting power from transparent photovoltaics. The Cu layer serves as seed layer for the two-dimensional growth of an Ag film. The AZO layer is used to enhance the optoelectrical properties of Cu/Ag. The AZO/Ag/Cu film exhibits a high visible transmittance of 83.1% and a sheet resistance of 18 Ω/□. Importantly, the proposed Cu/Ag/AZO transparent conductor enables the development of transparent and flexible NiO/ZnO-based photovoltaics with a power conversion efficiency of 1.14%. These results shows that the present system may be a promising platform for cost-effective and high-performance flexible optoelectronics.

Solution-processed polymer bilayer heterostructures as hole-transport layers for high-performance opaque and semitransparent organic solar cells

Interfacial layer materials such as hole-transport layers (HTLs) are critical to realizing high-performance organic solar cells (OSCs). However, most OSCs are relying on a prominent HTL material of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with the hygroscopic and acidic feature, which induces poor device stability and limited power conversion efficiencies (PCEs). Here, a novel type of HTLs is developed by combining intrinsically stable poly(triarylamine) (PTAA) with modified PEDOT:PSS for efficient opaque and semitransparent OSCs with good stability. Using diluted solution processing, isopropanol-diluted PEDOT:PSS (ID-PEDOT:PSS) is deposited onto hydrophobic PTAA to improve interfacial compatibility, thereby forming a fitted polymer bilayer heterostructure HTL of PTAA/ID-PEDOT:PSS with high film quality and good transparency. For applications in OSCs with a nonfullerene acceptor (M36), the resulting opaque devices deliver an improved PCE of 14.45%, much higher than 5.72% and 13.21% for the pure PTAA and PEDOT:PSS HTLs-based devices, respectively. The stability of the PTAA/ID-PEDOT:PSS-based OSCs is improved simultaneously, where a normalized PCE for the device after storage over three months retains above 80%, much better than those of devices with other two HTLs. This novel HTL is further used to achieve efficient and stable semitransparent M36-based devices for the first time, exhibiting an outstanding PCE of 12.34% at a high average visible transmittance of 25.56%. Our findings provide an excellent semiconducting interlayer candidate to develop promising opaque and semitransparent OSCs.

A Scalable, Robust Polyvinyl‐Butyral‐Based Solid Polymer Electrolyte with Outstanding Ionic Conductivity for Laminated Large‐Area WO3–NiO Electrochromic Devices

AbstractPolyvinyl butyral (PVB) is a well‐established polymer interlayer material that has been used in laminated safety glass panels for over 80 years. However, its intrinsically poor ionic conductivity (σ) severely restricts its widespread application as a solid polymer electrolyte (SPE) for laminated WO3–NiO electrochromic devices (ECDs). Here, a new strategy for significantly improving the σ of PVB via a cross‐linking reaction with 3‐glycidoxypropyltrimethoxysilane (KH560) is presented. The cross‐linked PVB‐SPE with 10 wt.% KH560 exhibits the highest room‐temperature σ value among the investigated samples (1.51 × 10−4 S cm−1), which is also higher than that of previously reported PVB‐based SPEs (10−5–10−7 S cm−1). Additionally, the prepared SPE exhibits comprehensive optical, mechanical, and thermal performances, including a high visible transmittance (>91%), relatively high adhesive strength (2.13 MPa), and superior thermal stability (up to 150 °C). Laminated WO3–NiO ECDs with dimensions of 5 × 5 cm2 and 20 × 20 cm2, fabricated by leveraging the aforementioned properties of the electrolyte, operate stably at temperatures ranging from −20 to 80 °C, underscoring the potential of the PVB‐SPE for realizing commercially viable large‐area ECDs.

One-step ball-milling synthesis of cesium tungsten bronze nanoparticles and near-infrared shielding performance

Tungsten bronze (MxWO3) materials have been widely used as thermal insulation for architectural glass because of their higher near-infrared (NIR) light shielding capacity. To solve the problems encountered in solvothermal preparation with high costs and low yields, this study has developed a facile, eco-friendly, effective, but low-cost method, with no need for any annealing process, for promoting the large-scale fabrication of cesium tungsten bronze (CsxWO3, x = 0.32) nanomaterials for potential thermal insulation windows applications. In the proposed ball-milling process, the tungstic acid material could be reduced to hydro tungsten bronze (HxWO3) by cellulose, while the cesium ions (Cs+) could be gradually incorporated into the interspace until the formation of Cs0.32WO3 (Cs/W atomic ratio = 0.32), with an average particle size of ∼33 nm after a 15 h ball-milling process. The reaction mechanism has been investigated in detail via particle structural analysis and optical performance characterization. The obtained Cs0.32WO3 nanoparticles are dispersed in a solution composed of surfactant (s) and polymer (s) which can form a thin film with a thickness of about 2 μm on a glass substrate, by a spinning coating or casting method, to exhibit high visible (Vis) light transmittance (T566nm = 72.6%), and excellent NIR-shielding capability (T1388nm = 5.3%), reflected by good heat-insulating performance in practice use. This work will pave a new path for large-scale production of Cs0.32WO3 nanomaterials with low costs and high performance, beneficial for practical applications in energy-saving glass coatings.

High Efficiency Transparent and Semi‐Transparent Photovoltaics Based on a Layer‐By‐Layer Deposition

Transparent and semitransparent photovoltaics offer an exciting opportunity to integrate existing infrastructure with renewable energy. Organic photovoltaics (OPVs) are key enablers for wavelength‐selective transparent photovoltaics (TPVs) because of their selective absorption in the near‐infrared (NIR) that enables simultaneously high power conversion efficiency (PCE) and average visible transmittance (AVT). The recent rise of OPVs and TPVs has been accelerated in large part by the development of nonfullerene acceptors (NFAs) as highly adaptable deep NIR harvesting materials. Herein, sequential layer‐by‐layer (LBL) deposition of a selectively NIR absorbing nontraditional acceptor polymer is paired with a NIR absorbing donor IEICO‐4F that is typically considered an NFA via solvent orthogonality. With detailed optimization of the active layers and top electrode, semi‐transparent photovoltaics with a PCE of 8.8%, AVT of 40.9%, and a light utilization efficiency of 3.6% are demonstrated. The LBL approach enables explicit optical modeling of the device structure to extract exciton diffusion lengths >100 nm for both the polymer and IEICO‐4F with a transition in charge collection length regimes dependent on the acceptor thickness. Furthermore, the LBL deposition technique enables an investigation of the full range of polymer thickness and its impact on power generation and optical performance.

Metafilms for visible and infrared compatible camouflage of high-temperature targets

With the rapid development of multispectral detection, infrared and visible compatible camouflage becomes necessary. Metafilms with dielectric/metal/dielectric (D/M/D) structures can be highly transparent in visible band (380 ∼ 780 nm) and highly reflective in infrared atmospheric windows (3 ∼ 5 μm, 8 ∼ 14 μm). The metafilm can be deposited on the equipment surface, and the high visible transmittance can make the original camouflage coating continue to achieve visible camouflage, while the low infrared emissivity can inhibit the infrared signal to achieve infrared camouflage. Compatible camouflage is urgently needed by high-temperature targets such as exhaust pipes and engine cabins. Therefore, the thermal stability of multilayer structure is very important. In this study, a D/M/D-structured metafilm with improved thermal performance is proposed. Al-doped zinc oxide (AZO) is selected as the material of the dielectric layers due to good thermal stability, and high visible transmittance is realized through the mechanism of admittance matching. Ag is selected as the material of the metal layer to increase infrared reflectance. The metafilm with the structure of AZO/Ag/AZO is rigorously designed and fabricated. The results from Fourier transform infrared spectrometer and spectrophotometer show that the integrated visible transmittance and infrared emissivity at room temperature is higher than 0.87 and lower than 0.05, respectively. The camouflage performance of the metafilm is demonstrated on a flexible polyethylene terephthalate (PET) substrate. The camouflage performance of metafilm samples at 20 ∼ 140 °C is tested on a model cabin. The metafilm does not affect the original camouflage coating, so it can achieve visible camouflage. The radiation temperature of the metafilm is approximately 80 °C lower than that of the control surface, and the infrared signature is significantly attenuated. In order to further investigate the thermal stability and thermal fatigue resistance of the metafilm, metafilm deposited on quartz substrate is continuously heated and periodically heated at different temperatures. It is found that the sample can withstand continuous heating at 450 °C for 4 h or repeated heating for 20 cycles. SEM (scanning electron microscope) and EDS (energy dispersive spectrometer) scanning shows that if heated at higher temperature or for more cycles, the AZO layer becomes blocky, and the proportion of Ag and O changes significantly. This leads to the decrease of visible transmittance and the increase of infrared emissivity of samples.

High work function thermally stable OMO-based transparent electrode for optoelectronic applications

Ultrathin metal films (UTMFs) have emerged as a potential contender as a transparent electrode (TE) in various optoelectronic applications. Oxide-metal-oxide (OMO) based TEs incorporating UTMFs are the new state-of-the-art approach towards fabricating high-performance indium-free TEs. Here, we have demonstrated an OMO-based indium-free TE utilizing nickel oxide (NiO) and silver (Ag) as oxide and metal films respectively. Optical constants of NiO and Ag obtained from spectroscopic ellipsometry have been utilized in determining the optimum thickness of alternate layers in the OMO stack using a MATLAB code based on the transfer matrix method. To minimize the reflection losses, 40 nm of NiO as films was deposited on either side of the Ag film. A highly transparent NiO/Ag/NiO (NAN) electrode has been obtained by the physical vapor deposition technique. The fabricated TE shows high transmittance >82% in the visible region along with a low sheet resistance below 6 Ω/□. To analyze the thermal stability of NAN-TE, it has been treated at different elevated temperatures. It was observed that NAN-TE shows better thermal stability in comparison to commercially available ITO-TE. The incorporation of NiO as an overcoat layer results in enhancing the work function to 5.35 eV as measured by Kelvin Probe Force Microscopy (KPFM). The high average visible transmittance, high work function, low sheet resistance, and high-temperature tolerance make the developed TE compatible with optoelectronic devices where high-temperature processing is necessary. To verify the same a bifacial perovskite solar cell is fabricated incorporating the NAN-TE as top TE and a power conversion efficiency (PCE) of 3.51% and 2.56% is obtained by illuminating the fabricated device from FTO and NAN side.