Flexible electronics aim to provide stretchable light-emitting devices for daily life capable of withstanding multiple stretch-relaxation cycles. In this paper, we present a stretchable green perovskite light electrochemical cell (PeLEC) with a CsPbBr3 active layer, where a vertically oriented GaP nanowire (NW) array combined with a pre-stretched uniaxial electrode based on single-walled carbon nanotubes (SWCNT) is used as a distributed stretch-resistant electrode. To achieve PeLEC stability, the array of NWs is embedded 1.5-2 & micro;m deep into the perovskite layer, while the total perovskite layer thickness is 2-3 & micro;m. Stretch-related electroluminescence (EL) measurements demonstrate a stable emission peak at 535 nm for initial and stretched device states with a threshold voltage of 8.5 V. The slight difference in the observed EL intensity after stretching can be explained by the changes in the CsPbBr3 film geometry, such as the increase of the space between perovskite crystals under uniaxial strain, which reduces the effective emissive volume within the device area, and by the partial restructuring of the SWCNT network. The impedance spectroscopy tests of the CsPbBr3 device show that although the lateral resistance increased by 7 times after more than 100 stretch-relaxation cycles (primarily due to cracking of the perovskite crystals), the operation current of the stretchable PeLEC does not significantly change. This mechanical stability is attributed to the GaP NW-based distributed electrode architecture, which efficiently accommodates perovskite crystal cracking. These results demonstrate the potential of the proposed stretchable PeLEC architecture for flexible and stretchable electronics.

The emergence of cesium lead halide perovskite materials stable at air opened new prospects for the optoelectronic industry.In this work we present an approach to fabricating a flexible green perovskite light-emitting electrochemical cell(PeLEC)with a CsPbBr3 perovskite active layer using a highly-ordered silicon nanowire(Si NW)array as a distributed electrode integrated within a thin polydimethylsiloxane film(PDMS).Numerical simulations reveal that Si NWs-based distributed elec-trode aids the improvement of carrier injection into the perovskite layer with an increased thickness and,therefore,the enhance-ment of light-emitting performance.The X-ray diffraction study shows that the perovskite layer synthesized on the PDMS mem-brane with Si NWs has a similar crystal structure to the ones synthesized on planar Si wafers.We perform a comparative analy-sis of the light-emitting devices'properties fabricated on rigid silicon substrates and flexible Si NW-based membranes released from substrates.Due to possible potential barriers in a flexible PeLEC between the bottom electrode(made of a network of sin-gle-walled carbon nanotube film)and Si NWs,the electroluminescence performance and I ̶ V properties of flexible devices deteri-orated compared to rigid devices.The developed PeLECs pave the way for further development of inorganic flexible uniformly light-emitting devices with improved properties.

As alternatives to conventional perovskite light-emitting diodes, perovskite light-emitting electrochemical cells (PeLECs) are in great demand in modern science and technology due to their simplified structure and attainable higher luminance. Here, for the first time, we present the implementation and characterization of red CsPbIBr2-based PeLECs/LEDs. To improve perovskite material phase stability, we applied the following strategies for mitigating the mixed anion lead halide perovskite phase segregation: Pb2+ partial substitution by Mn2+, boundary passivation by poly(ethylene oxide) with polyvinylidene fluoride, and two-step thermal treatment with vacuuming and annealing. The complex measurements of photoluminescence, optical density, energy-dispersive X-ray spectroscopy, and X-ray diffraction confirm the minor phase segregation in the optimized perovskite layers. The performed ab-initio calculations predicted the band gaps of perovskite materials with a mixed anion composition, corresponding well to the results of optical measurements. Finally, current and electroluminescence time tracking proved the formation of a dynamic p-i-n structure in the studied PeLEC devices. The developed PeLECs/LEDs exhibited relatively high, for red PeLECs, electroluminescence up to 96 cd m-2 with a peak position at 667-672 nm.

We report the approach to designing the hybrid gas sensor based on the array of vertically-oriented InAs nanowires and gas-permeable film made of single-walled carbon nanotubes (SWCNTs). We probe the sensor performance at room temperature towards isopropyl alcohol analyte, whose highest occupied molecular orbital energy to be in-between the Fermi levels of SWCNTs and InAs, to check the main contributing mechanism. Our theoretical analysis revealed that electronic systems of both materials contribute to sensor response. Our findings indicate that the sensor response to isopropyl alcohol in a mixture with dry and humid air primarily stems from its interaction with carbon nanotubes, although it also involves an interplay between the electron energy states of SWCNTs and InAs. We also test the sensor response to methanol, ethanol, and butanol analytes and demonstrate that it enhances with a molecule weight. The proposed sensor design can be further optimized to capture vector signals under a multivariate approach to selectively determine various analytes.

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In this paper, we report a method to estimate the average length of bundles in a randomly oriented network of single-walled carbon nanotubes (SWCNTs) by analyzing the dependence of its sheet resistance on the distance between contacts. We propose an analytical model to verify the method and find the model's limitations using Monte Carlo simulations. Then, we apply the proposed approach to experimental results acquired from 95% (at 550 nm wavelength) transparent SWCNT films. The proposed method to estimate the average SWCNT bundle length can be used in situ and does not require any specific sample preparation step that can distort the SWCNT network.

We report a new two-layer polysiloxane (PMHS/PDMS) halide perovskite encapsulation approach that allows operation of perovskite light-emitting devices under high humidity (80% RH) conditions and improves their performance due to finite water diffusion.

In this paper we describe a new method to improve properties of a perovskite light-emitting electrochemical cell (PeLEC) by double layer polymer encapsulation. Our per-ovskite devices include 1) CsPbBr3-poly(ethylene oxide) layer as emissive layer, 2) NiOx:Cu nanoparticles layer as hole transport layer, 3) a transparent single wall carbon nanotubes as an electrode of the structure and 4) a double layer encapsulation polymer layers. These encap-sulation layers consist of metal catalyst-free cross-linked polymethylhydrosiloxane and poly-dimethylsiloxane Sylgard 184. After 168 hours of aging in 80% relative humidity conditions an increase in luminance and in photo luminance quantum yield of our devices was detected. Our encapsulation provides optimal exposure of water vapor on perovskite material, which improves device properties by partial phase transition of CsPbBr3 to Cs4PbBr6, which has been confirmed by X-ray diffraction method. The Cs4PbBr6 passivate CsPbBr3 crystals and then the polymethylhydrosiloxane layer does not allow agglomeration of perovskite grains. The poly-dimethylsiloxane layer is required as a mechanical supporting layer. The polymethylhydrosilox-ane/polydimethylsiloxane encapsulation of perovskite devices reveals a promising new way of development of flexible and stretchable perovskite light-emitting devices, which can work in extreme humid conditions.

The films of single-walled carbon nanotubes (SWCNTs) are a promising material for flexible transparent electrodes, which performance depends not only on the properties of individual nanotubes but also, foremost, on bundling of individual nanotubes. This work investigates the impact of densification on optical and electronic properties of SWCNT bundles and fabricated films. Our ab initio analysis shows that the optimally densified bundles, consisting of a mixture of quasi-metallic and semiconducting SWCNTs, demonstrate quasi-metallic behavior and can be considered as an effective conducting medium. Our density functional theory calculations indicate the band curving and bandgap narrowing with the reduction of the distance between nanotubes inside bundles. Simulation results are consistent with the observed conductivity improvement and shift of the absorption peaks in SWCNT films densified in isopropyl alcohol. Therefore, not only individual nanotubes but also the bundles should be considered as building blocks for high-performance transparent conductive SWCNT-based films.

This paper demonstrates an elastic (i.e., both flexible and stretchable) pixel matrix based on the patterned films of single-walled carbon nanotubes, which were obtained using optical lithography and plasma etching. The proposed elastic electrodes maintain their initial resistivity at 10% stretching. We also demonstrate an application of the elastic pixel matrix to an array of III–V semiconductor nanowires encapsulated into the elastic polymer matrix, which paves the way for highly deformable inorganic light-emitting or photodetector devices.

In this work, we propose and realize new design strategies for flexible solar cells based on the classical GaAs/AlGaAs heterojunction. The InAlP layer was chosen as a sacrificial layer for lift-off process in order to separate the heterostructure from the substrate, we also used poly (methyl methacrylate)membrane as a flexible substrate. The combination of these design strategies made it possible to achieve relativley high specific power --- 778 W/kg. Keywords: solar cell, GaAs, ELO, flexible electronics.

In this work, we propose and realize new design strategies for flexible solar cells based on the classical GaAs/AlGaAs heterojunction. The InAlP layer was chosen as a sacrificial layer for lift-off process in order to separate the heterostructure from the substrate, we also used poly (methyl methacrylate)membrane as a flexible substrate. The combination of these design strategies made it possible to achieve relativley high specific power - 778 W/kg.

Light-excited flexible and self-healing luminescent polymers have attracted extensive attention for developing advanced color-emitting films. Luminophores on the base of lanthanide(III)-incorporating polysiloxanes exhibit a high photoresponse and can be applied for controlled color lighting in flexible device applications. We present red-, green-, and blue-emitting Eu3+, Tb3+, and Tm3+-bipyridinedicarboxamide-co-polydimethylsiloxanes (Ln-Bipy-PDMS) produced with a two-step procedure of polycondensation and complexation. Bipyridinic ligands provide formation of coordinatively saturated complexes of lanthanide ions and strong photoluminescence (PL) in the case of Eu3+ and Tb3+. The thin Ln-BipyPDMS films are studied as ultraviolet-light converters, which can be mechanically stacked one above another to achieve the desired color. We demonstrate that these stacks can have intense PL in the spectral range from green to yellow and red. Due to the structural features, Ln-Bipy-PDMS also demonstrate a relatively high tensile (approximately 1.5 MPa) and elongation at break (approximately 185%) and non-autonomous self-healing on heating. The self-healing properties of Ln-Bipy-PDMS enable the stacking of films into monoliths with the required color of PL. Such systems do not require any synthesis stages, and a one-healed monolith film possesses two luminescence colors.

The direct integration of epitaxial III-V and III-N heterostructures on Si substrates is a promising platform for the development of optoelectronic devices. Nanowires, due to their unique geometry, allow for the direct synthesis of semiconductor light-emitting diodes (LED) on crystalline lattice-mismatched Si wafers. Here, we present molecular beam epitaxy of regular arrays n-GaN/i-InGaN/p-GaN heterostructured nanowires and tripods on Si/SiO2 substrates prepatterned with the use of cost-effective and rapid microsphere optical lithography. This approach provides the selective-area synthesis of the ordered nanowire arrays on large-area Si substrates. We experimentally show that the n-GaN NWs/n-Si interface demonstrates rectifying behavior and the fabricated n-GaN/i-InGaN/p-GaN NWs-based LEDs have electroluminescence in the broad spectral range, with a maximum near 500 nm, which can be employed for multicolor or white light screen development.

The technology of creating patterned flexible electrodes based on single-walled carbon nanotubes and polydimethylsiloxane was demonstrated in this paper. A series of experiments were carried out to study whether the percolation affects the conductivity of patterned SWCNT layers. It was found that in patterns with the linewidth above 1 μm and the cell size above 50 μm the random character of SWCNT networks may be neglected. The impact of bending on the grid conductivity was studied. We observed a very moderate increase of resistance below 5% under the strain up to 4 %, which is comparable with the previous results for continuous SWCNT layers and shows the improvement in comparison with the previous reports on patterned SWCNT layers.

The length of single-walled carbon nanotubes (SWCNTs) affects the optoelectronic and mechanical properties of macroscopic SWCNT layers. Modern methods are capable to measure the length of short nanotubes, and also require complex sample preparation procedures. In this work we show that the average length of SWCNTs can be estimated by measuring the resistance of randomly oriented SWCNTs array. We observe the change in the slope of the resistance dependence on the distance between the contacts with the interval between 100 and 200 μm. The change of resistance slope indicates a change in the path of current flow through the SWCNT. The change in the conduction path can be associated with the “effective bundle length”, which should be related to the average nanotube length. Thus, we have demonstrated a simple and quick technique to measure SWCNT bundle length, which can be used in-situ and does not require special sample preparation.

We propose and demonstrate both flexible and stretchable blue light-emitting diodes based on core/shell InGaN/GaN quantum well microwires embedded in polydimethylsiloxane membranes with strain-insensitive transparent electrodes involving single-walled carbon nanotubes. InGaN/GaN core-shell microwires were grown by metal-organic vapor phase epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films can stand up to 20% stretching while maintaining efficient operation. Membrane-based LEDs show less than 15% degradation of electroluminescence intensity after 20 cycles of stretching thus opening an avenue for highly deformable inorganic devices.

In this paper, the theoretical study of LED based on GaN NWs with carbon nanotubes (CNT) top contact has been presented. The main electrical and optical characteristics of LED have been numerically calculated. In a 0.5 x 0.5 mm NWs array, the Ohmic losses in CNTs were 2.7% with an operating current density of 50 A/cm 2 . It proves the possibility of using CNTs as transparent contact.

This work is devoted to fabrication and characterization of a GaAs solar cell with a CNT top contact. The characteristics of a conventional solar cell with a metal contact grid and a solar cell with a CNT electrode were compared to demonstrate the benefits of a CNT based approach. The photoelectric properties of the solar cells were studied by measuring the IV characteristics and external quantum efficiency. The fabricated CNT solar cell showed better performance due to improved photocurrent collection efficiency. The demonstrated technology for the fabrication of CNT electrodes can be applied to a wide range of semiconductor photovoltaic devices, including flexible thin-film solar cells and solar cells based on nanowires.