Rigid Glass Substrates Research Articles

GABr Post-Treatment for High-Performance MAPbI3 Solar Cells on Rigid Glass and Flexible Substrate.

Perovskite solar cells have exhibited astonishing photoelectric conversion efficiency and have shown a promising future owing to the tunable content and outstanding optoelectrical property of hybrid perovskite. However, the devices with planar architecture still suffer from huge Voc loss and severe hysteresis effect. In this research, Guanidine hydrobromide (GABr) post-treatment is carried out to enhance the performance of MAPbI3 n-i-p planar perovskite solar cells. The detailed characterization of perovskite suggests that GABr post-treatment results in a smoother absorber layer, an obvious reduction of trap states and optimized energy level alignment. By utilizing GABr post-treatment, the Voc loss is reduced, and the hysteresis effect is alleviated effectively in MAPbI3 solar cells. As a result, solar cells based on glass substrate with efficiency exceeding 20%, Voc of 1.13 V and significantly mitigated hysteresis are fabricated successfully. Significantly, we also demonstrate the effectiveness of GABr post-treatment in flexible device, whose efficiency is enhanced from 15.77% to 17.57% mainly due to the elimination of Voc loss.

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

GABr post-treatment for high-performance MAPbI3 solar cells on rigid glass and flexible substrate

Metalloporphyrin-Based Metal-Organic Frameworks on Flexible Carbon Paper for Electrocatalytic Nitrite Oxidation.

Deposition of redox-active metal-organic frameworks (MOFs) as thin films on conductive substrates is of great importance to improve their electrochemical performance and durability. In this work, a series of metalloporphyrinic MOF crystals was successfully deposited as thin films on carbon fiber paper (CFP) substrates, which is an alternative to rigid glass substrates. The specific dimensions of the obtained films could be adjusted easily by simple cutting. Metalloporphyrinic MOFs on CFP with different active metal species have been employed for electrochemical conversion of the carcinogenic nitrite into the less toxic nitrate. The MOFs on CFP exhibit remarkable improvement in terms of the electrocatalytic performance and reusability compared with the electrodes prepared from MOF powder. The contribution from metal species of the porphyrin units and reaction mechanisms was elucidated based on the findings from X-ray photoelectron spectroscopy (XPS) and in situ X-ray absorption near edge structure (XANES) measured during the electrochemical reaction. By integrating the redox-active property of metalloporphyrinic MOFs and high conductivity of CFP, MOF thin films on CFP provided a significant improvement of electrocatalytic performance to detoxify the carcinogenic nitrite with good stability.

Implementation of a nanochannel open/close valve into a glass nanofluidic device

In micro-/nanofluidics, channel open/close valves are fundamental to integrating fluid operations and realizing highly integrated analytical devices. Recently, we proposed a nanochannel open/close valve utilizing glass deformation and verified the principle of opening and closing nanochannels. Glass deformation sufficient to close the valve was achieved using a 45-µm-thick glass sheet as a material of a nanofluidic device. However, since the device incorporates the thin glass sheet and is not robust enough to be used for repeated analyses, fluid operations utilizing the valve have not been verified sufficiently. Thus, in the present study, we fabricated a nanofluidic device implemented with a nanochannel open/close valve using rigid glass substrates of thicknesses on the order of 100 μm, and verified fluid operations utilizing the valve. On a small part of the substrate, we designed and fabricated a 30-µm-thick deformation section for the valve. The open/close operation and the performance of the valve were verified. The leakage of the valve was measured to be 2%, the response time was 0.9 s, and the number of repetitions was over 100,000. By utilizing the fabricated valve, we demonstrated fluid operations with femtoliter to picoliter volumes. Flow-switching within approximately 1 s and a flow control rate in the 63-1341 fL/s range was achieved. In addition, the fluid resistance of the valve was investigated both experimentally and numerically to establish a guideline for designing the valve. The valve developed and the design guidelines obtained will greatly contribute to integrated nanofluidic analytical devices.

Flexible perovskite solar cells based on indium-free AZO/Ag/AZO multilayer transparent electrodes

<p indent=0mm>Perovskite solar cells (PSCs) fabricated on transparent polymer substrates are considered to be one of the most disruptive competitors in the solar cell industry for their favorable traits, including high efficiency, flexibility, light weight, portability, and compatibility with curved surfaces. More importantly, PSCs based on transparent polymer substrates could dramatically lower down the processing cost, by introducing high-throughput roll-to-roll manufacturing and low-temperature energy-saving technological processes. However, due to the low glass transition temperatures of common transparent polymer substrates, it is difficult to prepare the traditional transparent electrodes such as indium tin oxide (ITO) and fluorine doped SnO₂ (FTO) and the electron transport layer with efficient charge transport to meet the specifications of flexible PSCs as on rigid glass substrate, which has become a major bottleneck to improve the device performance of flexible PSCs based on transparent polymer substrates. In this paper, multilayer films of AZO/Ag/AZO are deposited onto heat-sensitive polyethylene terephthalate (PET) substrate by radio frequency magnetron sputtering technique at room temperature to develop indium-free flexible transparent conductive films (TCFs), which are utilized as transparent electrode to prepare flexible PSCs with planar regular structure. The effects of Ag mid-layer thickness on microstructure and photoelectric properties of the AZO/Ag/AZO multilayer films are investigated by scanning electron microscopy, UV-VIS transmission spectra and four-point probe resistance measurements. It is found that when Ag layer thickness is less than <sc>5 nm,</sc> Ag layer has the island structure and the electrical connection is very poor, so that the samples have a higher sheet resistance. As the thickness of Ag layer is increased, the Ag layer changes gradually from discontinuous structure to continuous structure, the sheet resistances of the samples decrease drastically. However, when the thickness of Ag layer is beyond <sc>9 nm,</sc> the sheet resistances of the samples decrease slowly with further increasing the thickness of Ag layer. The analysis of optical transmission spectra indicates that with increasing the Ag layer thickness, the average transmittance in the visible light range of the AZO/Ag/AZO multilayer films increases first and then decreases. The Haacke figure of merit has been calculated for the AZO/Ag/AZO multilayer films. The best Haacke figure of merit of 2.3×10^–2Ω^–1 is obtained for the 11-nm-thick Ag mid-layer sample, which has an average transmittance of 83.3% in the spectral range of <sc>400–800 nm</sc> and a sheet resistance of 7.0 Ω/sq. In addition, the bending test indicates that the developed AZO/Ag/AZO multilayer TCFs also have excellent mechanical flexibility, and the relative change rate of sheet resistance is less than 8% after 1000 bending cycles with a <sc>5-mm</sc> bending radius. The flexible PSCs are fabricated with a configuration of Ag/MoO₃/spiro-OMeTAD/perovskite/SnO₂/AZO/Ag/AZO on PET substrates. The mixed cation and mixed halide perovskite films are prepared by a single step inverse solvent crystallization method. Considering that SnO₂ layer presents advantages of low-temperature processability and modulating the band level mismatch at the interface between the AZO/Ag/AZO and the perovskite layer, SnO₂ electron transport layer is fabricated by spin-coating the aqueous soluble SnO₂ nanoparticles and annealing at a low temperature of 120°C. The flexible PSC based on the optimized AZO/Ag/AZO transparent electrode achieves power conversion efficiency (PCE) of 11.9%. At a bending radius of <sc>10 mm,</sc> flexible PSC based on AZO/Ag/AZO multilayer electrodes maintains 95% of their initial PCE even after 100 bending cycles.

Gold Nanoparticle Films Deposited on Substrates From Brij 30 Reverse Micellar Solution: Formation, Processing, and Characterization

The study addresses layer-by-layer formation processes and properties of gold nanoparticle films deposited from reverse micellar solutions of Brij 30 surfactant on rigid glass and flexible polymer (PET) substrates. The films are of interest for transparent electronics and optical sensorics. The spectrophotometric studies of film formation revealed linear relationships between the extinction of growing film at definite wavelengths and the number of nanoparticle deposition cycles, and their parameters were determined. The effects of concentrations of gold and 1,2-ethanedithiol as an interlayer linker in the initial solutions on the film growth were elucidated. Data on the composition, morphology, optical spectra, and surface resistance of gold nanoparticle films, and changes of these characteristics during heat treatment in air and in boiling ethanol were gained using X-ray diffractometry, scanning electron and atomic force microscopy, UV-Vis spectroscopy, and electrical resistance measurements.

Traction Forces Control Cell-Edge Dynamics and Mediate Distance Sensitivity during Cell Polarization.

Traction forces are generated by cellular actin-myosin system and transmitted to the environment through adhesions. They are believed to drive cell motion, shape changes, and extracellular matrix remodeling [1-3]. However, most of the traction force analysis has been performed on stationary cells, investigating forces at the level of individual focal adhesions or linking them to static cell parameters, such as area and edge curvature [4-10]. It is not well understood how traction forces are related to shape changes and motion, e.g., forces were reported to either increase or drop prior to cell retraction [11-15]. Here, we analyze the dynamics of traction forces during the protrusion-retraction cycle of polarizing fish epidermal keratocytes and find that forces fluctuate together with the cycle, increasing during protrusion and reaching maximum at the beginning of retraction. We relate force dynamics to the recently discovered phenomenological rule [16] that governs cell-edge behavior during keratocyte polarization: both traction forces and probability of switch from protrusion to retraction increase with the distance from the cell center. Diminishing forces with cell contractility inhibitor leads to decreased edge fluctuations and abnormal polarization, although externally applied force can induce protrusion-retraction switch. These results suggest that forces mediate distance sensitivity of the edge dynamics and organize cell-edge behavior, leading to spontaneous polarization. Actin flow rate did not exhibit the same distance dependence as traction stress, arguing against its role in organizing edge dynamics. Finally, using a simple model of actin-myosin network, we show that force-distance relationship might be an emergent feature of such networks.

Fabrication and characterization of thin-film silicon resonators on 10 m-thick polyimide substrates

MEMS fabricated on polymer substrates can allow for a range of new applications that require bending or lightweight, unbreakable substrates. The surface micromachining of hydrogenated amorphous silicon resonators on 10 µm-thick flexible polyimide substrates is presented. Clamped-clamped (bridges) and clamped-free (cantilevers) resonators are fabricated and characterized, exhibiting quality factors as high as 2.0 × 103 and natural resonance frequencies in the 104–106 Hz range. The deflection of an 80 µm long bridge was measured to be over 100 pm, using laser Doppler vibrometry. The electrical addressing of the devices was demonstrated to be reliable when bent to radii of curvature larger than 10 mm. The resonators on ultra-thin polymer are characterized using different actuation voltages and pressures, showing comparable performance to resonators on rigid (glass) substrates. However, the flexible substrate allows the relaxation of the residual stress of the structural film in clamped-clamped structures, lowering the resonance frequency. Resonators on PI were found to be suitable for mass-sensing applications, achieving a minimum frequency shift detectable Δfmin = 30 Hz which results in a calculated mass sensitivity of 25 pg in vacuum. Ultimately, the reliable performance of the resonators developed in this work make them good candidates for applications that require mass-sensing on ultra-thin, flexible substrates.

Integrin Binding Dynamics Modulate Ligand-Specific Mechanosensing in Mammary Gland Fibroblasts.

SummaryThe link between integrin activity regulation and cellular mechanosensing of tissue rigidity, especially on different extracellular matrix ligands, remains poorly understood. Here, we find that primary mouse mammary gland stromal fibroblasts (MSFs) are able to spread efficiently, generate high forces, and display nuclear YAP on soft collagen-coated substrates, resembling the soft mammary gland tissue. We describe that loss of the integrin inhibitor, SHARPIN, impedes MSF spreading specifically on soft type I collagen but not on fibronectin. Through quantitative experiments and computational modeling, we find that SHARPIN-deficient MSFs display faster force-induced unbinding of adhesions from collagen-coated beads. Faster unbinding, in turn, impairs force transmission in these cells, particularly, at the stiffness optimum observed for wild-type cells. Mechanistically, we link the impaired mechanotransduction of SHARPIN-deficient cells on collagen to reduced levels of collagen-binding integrin α11β1. Thus integrin activity regulation and α11β1 play a role in collagen-specific mechanosensing in MSFs.

Biowaste-Derived, Self-Organized Arrays of High-Performance 2D Carbon Emitters for Organic Light-Emitting Diodes.

Low-cost flexible organic light-emitting diodes (OLEDs) with nanoemitter material from waste open up new opportunities for sustainable technology. The common emitter materials generated from waste are carbon dots (CDs). However, these have poor luminescent properties. Further solid-state emission quenching makes application in display devices challenging. Here, flexible and rigid OLED devices are demonstrated using self-assembled 2D arrays of CDs derived from waste material, viz., human hair. High-performance CDs with a quantum yield (QY) of 87%, self-assembled into 2D arrays, are achieved by improving the crystallinity and decreasing the CDs' size distribution. The CD island array exhibits ultrahigh hole mobility (≈10-1 cm2 V-1 s-1 ) and significant reduction in solid-state emission quenching compared to pristine CDs; hence, it is used here as an emitting layer in both indium tin oxide (ITO)-coated glass and ITO-coated flexible poly(ethylene terephthalate) (PET) substrate OLED devices, without any hole-injection layer. The flexible OLED device exhibits a stable, voltage-independent blue/cyan emission with a record maximum luminescence of 350 cd m-2 , whereas the OLED device based on the rigid glass substrate shows a maximum luminescence of 700 cd m-2 . This work sets up a platform to develop next-generation OLED displays using CD emitters derived from the biowaste material.

Sputtered high perpendicular magnetic anisotropy CoPt thin film on flexible substrate at low temperature

In this study, CoPt alloy thin films with alternative sputtering of 0.4 nm-Co and 0.5 nm-Pt layers, [Co0.4/Pt0.5]n, on Pt underlayers were sputtered on rigid glass and soft PI (Polyimide) substrates at 100°C. The effects of repetition (n) of the [Co0.4/Pt0.5]n films on the magnetic properties and microstructures of [Co0.4/Pt0.5]n films were investigated. Results showed that [Co0.4/Pt0.5]4 film had a high perpendicular magnetic anisotropy (PMA (S⊥&amp;gt;0.98)) and a magnetocrystalline anisotropy constant (Ku∼1.12×107 erg/cm3), which were close to the properties of L11-CoPt film prepared at higher temperatures (∼300°C) as seen in previous works. Increasing repetition also increased residual stress and further reduced perpendicular magnetic properties. Thus, better magnetic properties would be obtained in the thinner case. The outstanding PMA properties of CoPt film still well kept as the rigid glass was replaced by flexible PI substrate. In this work, perpendicular magnetic CoPt film could be prepared at lower temperatures (∼100°C) on soft PI substrate. It strongly enhanced low temperature applications of hard magnetic alloy thin films, such as magnetic electronic components with high Ku and PMA on flexible substrate.

Scalable fabrication of organic solar cells based on non-fullerene acceptors

Organic solar cells have recently experienced a substantial leap in power conversion efficiency, in part driven by formulations with new non-fullerene acceptors. This has brought the technology past the psychologically important mark of 15% efficiency for unscaled laboratory devices, and the results are stimulating another burst of research activity. Whether this will propel the technology into a viable commercial contender has yet to be determined, but to realize the potential of organic solar cells for utility scale application, fabrication using scalable processing techniques has to be demonstrated—otherwise, the passing of the 15% mark will eventually leave no more lasting impact than what the passing of the 10% mark did. Thus, addressing the scaling lag between the 15% cell efficiencies of lab-scale devices on rigid glass substrates fabricated using non-scalable techniques and the 7% efficiencies of scalably fabricated devices on flexible substrates is key. Here, we discuss the concept of scalability and give an account of the literature on non-fullerene acceptor devices fabricated with scalable methods and materials. On the basis of this, we identify three crucial focus points for overcoming the lab-to-fab challenge: (i) dual temperature control, i.e. simultaneous control of the ink and substrate temperatures during deposition, (ii) systematic in situ morphology studies of active layer inks with new, green solvent formulations during continuous deposition, and (iii) development of protocols for continuous solution processing of smooth, transparent interfacial layers with efficient charge transfer to the active layer. Combining these efforts and in general accompanying such studies with stability analyses and fabrication of large-area, scalably processed devices are believed to accelerate the relevance of organic solar cells for large-scale energy supply.

Development of Highly Bendable Transparent Window Electrodes Based on MoOx, SnO2, and Au Dielectric/Metal/Dielectric Stacks: Application to Indium Tin Oxide (ITO)-Free Perovskite Solar Cells

Indium-doped tin oxide (ITO) is the transparent conductive material of choice for a wide range of optoelectronic devices such as sensors, light-emitting diodes and solar cells. However, its brittle nature, high cost, scarcity as well as aggressive deposition via sputtering determine the need to find cheap alternatives with high optical transparency, low sheet resistance, and mechanical flexibility. Dielectric/metal/dielectric (D/M/D) electrodes fulfill all these requirements and are deposited via low embodied energy low-temperature processing. We developed D/M/D multilayered electrodes based on thermally evaporated MoOx or solution-processed SnO2 seed layers, a thermally evaporated ultrathin Au film, and a spin-coated SnO2 top layer on rigid glass substrates. We first systematically unraveled the role of each layer on the resistance-transmittance properties of the full D/M/D electrode structure. By optimizing the thickness of the seed, metal and the top layer, we obtained electrodes with transmittance of 72% at 550 nm and a minimum sheet resistance of 9  sq-1. Subsequently, these optimized multilayered stacks were employed as bottom electrodes for perovskite solar cells with glass/D/M/D/mesoporous-TiO2/CH3NH3PbI3/spiro-MeOTAD/Au device architecture, delivering power conversion efficiencies (PCE) of 10.7%. Further, we deposited and characterized D/M/D electrodes on flexible polyethylene terephthalate (PET) films, achieving a maximum PCE of 7.6%. The difference in performance compared to rigid glass devices can be ascribed to the different wetting of the active layer on PET substrates. Flexible D/M/D electrodes displayed excellent mechanical properties compared to commercial PET/ITO, showing completely stable sheet resistance after repeated bending even down to 1.5 mm of curvature radius, whereas PET/ITO showed one order of magnitude increase in sheet resistance in the same mechanical test, due to formation of cracks in the conductive oxide. Our optimized D/M/D stacks on glass and especially on PET or other flexible substrates are therefore excellent alternatives to ITO as transparent window electrodes for low-cost, light-weight and conformal optoelectronics applications.

All‐Solution‐Processed Organic–Inorganic Hybrid Perovskite Light‐Emitting Diodes under Ambient Air

Herein, all‐solution‐processed and ambient air‐stable perovskite light‐emitting diodes (PeLEDs) based on organic–inorganic hybrid perovskite nanocrystals are fabricated. Uniform surface coverage of methylammonium lead bromide (MAPbBr3) perovskite nanocrystals fabricated under ambient air conditions is achieved by blowing nitrogen (N2) gas onto the surface of the perovskite–polymer‐mixed precursor solution as it is being spin‐coated and thus controlling the crystallization rate of the nanocrystals. To obtain uniform morphology, the experimental conditions are optimized, namely, the spin rate and N2 gas blowing start time. Finally, a spin rate of 5000 rpm (revolutions per minute) and N2 gas blowing for 10 s at 10 s after the start of spinning are found to be the optimal conditions. PeLEDs fabricated using the optimized N2 blowing conditions provide a high maximum luminance (L) of approximately 11 610 cd m−2 and a current efficiency of approximately 4.42 cd A−1 at an L of 2328 cd m−2 accompanied by excellent operational stability. The PeLEDs are not only fabricated on rigid glass substrates but also on polymeric and elastomeric substrates, which demonstrates their potential application as flexible and wearable devices.

Interfacial Energy Level Tuning for Efficient and Thermostable CsPbI2Br Perovskite Solar Cells.

Inorganic mixed‐halide CsPbX3‐based perovskite solar cells (PeSCs) are emerging as one of the most promising types of PeSCs on account of their thermostability compared to organic–inorganic hybrid counterparts. However, dissatisfactory device performance and high processing temperature impede their development for viable applications. Herein, a facile route is presented for tuning the energy levels and electrical properties of sol–gel‐derived ZnO electron transport material (ETM) via the doping of a classical alkali metal carbonate Cs2CO3. Compared to bare ZnO, Cs2CO3‐doped ZnO possesses more favorable interface energetics in contact with the CsPbI2Br perovskite layer, which can reduce the ohmic loss to a negligible level. The optimized PeSCs achieve an improved open‐circuit voltage of 1.28 V, together with an increase in fill factor and short‐circuit current. The optimized power conversion efficiencies of 16.42% and 14.82% are realized on rigid glass substrate and flexible plastic substrate, respectively. A high thermostability can be simultaneously obtained via defect passivation at the Cs2CO3‐doped ZnO/CsPbI2Br interface, and 81% of the initial efficiency is retained after aging for 200 h at 85 °C.

Efficient indoor p-i-n hybrid perovskite solar cells using low temperature solution processed NiO as hole extraction layers

Hybrid perovskites have received tremendous attention due to their exceptional photovoltaic and optoelectronic properties. Among the two widely used perovskite solar cell device architectures of n-i-p and p-i-n, the latter is interesting in terms of its simplicity of fabrication and lower energy input. However this structure mostly uses PEDOT:PSS as a hole transporting layer which can accelerate the perovskite solar cell degradation. Hence the development of stable, inorganic hole extraction layers (HEL), without compromising the simplicity of device fabrication is crucial in this fast-growing photovoltaic field. Here we demonstrate a low temperature (~100 °C) solution - processed and ultrathin (~6 nm) NiO nanoparticle thin films as an efficient HEL for CH3NH3PbI3 based perovskite solar cells. We measure a power conversion efficiency (PCE) of 13.3% on rigid glass substrates and 8.5% on flexible substrates. A comparison with PEDOT:PSS based MAPbI3 solar cells (PCE ~ 7.9%) shows that NiO based solar cells have higher short circuit current density and improved open circuit voltage (1.03 V). Apart from the photovoltaic performance under 1 Sun, the efficient hole extraction property of NiO is demonstrated for indoor lighting as well with a PCE of 23.0% for NiO based CH3NH3PbI2.9Cl0.1p-i-n solar cells under compact fluorescent lighting. Compared to the perovskite solar cells fabricated on PEDOT:PSS HEL, better shelf-life stability is observed for perovskite solar cells fabricated on NiO HEL. Detailed microstructural and photophysical investigations imply uniform morphology, lower recombination losses, and improved charge transfer properties for CH3NH3PbI3 grown on NiO HEL.

Surface Plasmon‐Assisted Transparent Conductive Electrode for Flexible Perovskite Solar Cells

AbstractFlexible perovskite solar cells (PeSCs) possess the extraordinary potential in the applications of portable power sources and wearable electronics because of their superiorities in ease fabrication and efficient power conversion. These features are reinforced when a transparent conductive electrode with good flexibility is achieved. A unique electrode based on Ag periodic mesh (APM) perforated with hexagonal close‐packed nanoholes is proposed, showing a square resistance of ≈19.0 Ω sq−1 and optical transmittance of 66.0% in the whole visible region. PeSCs made on the optimal APM electrode with a rigid glass substrate achieve over twofold of photocurrent as compared to the counterpart on flat Ag film, resulting in a maximum power conversion efficiency of 17.06%. Experimental and theoretical characterizations indicate that the performance enhancement is mainly ascribed to the surface plasmon‐assisted extraordinary transmission enhancement and the scattering of incident light. Furthermore, the APM electrode enables PeSCs that are not only efficient but also highly flexible against bending deformation. Flexible PeSCs on plastic remain 90% of their initial efficiency after 1500 bending cycles with a bending radius of 3.0 mm. It is anticipated that the APM electrode with unique light coupling abilities provides a facile design route to achieving efficient and flexible PeSCs.