Showing papers on "Indium tin oxide published in 2016"

Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers

Abstract: Lead halide perovskite solar cells have recently attracted tremendous attention because of their excellent photovoltaic efficiencies. However, the poor stability of both the perovskite material and the charge transport layers has so far prevented the fabrication of devices that can withstand sustained operation under normal conditions. Here, we report a solution-processed lead halide perovskite solar cell that has p-type NiOx and n-type ZnO nanoparticles as hole and electron transport layers, respectively, and shows improved stability against water and oxygen degradation when compared with devices with organic charge transport layers. Our cells have a p–i–n structure (glass/indium tin oxide/NiOx/perovskite/ZnO/Al), in which the ZnO layer isolates the perovskite and Al layers, thus preventing degradation. After 60 days storage in air at room temperature, our all-metal-oxide devices retain about 90% of their original efficiency, unlike control devices made with organic transport layers, which undergo a complete degradation after just 5 days. The initial power conversion efficiency of our devices is 14.6 ± 1.5%, with an uncertified maximum value of 16.1%. Using metal oxides for both the hole- and electron-transport layers in perovskite solar cells significantly improves their stability compared with devices containing organic transport layers.

Large optical nonlinearity of indium tin oxide in its epsilon-near-zero region

Abstract: Nonlinear optical phenomena are crucial for a broad range of applications, such as microscopy, all-optical data processing, and quantum information. However, materials usually exhibit a weak optical nonlinearity even under intense coherent illumination. We report that indium tin oxide can acquire an ultrafast and large intensity-dependent refractive index in the region of the spectrum where the real part of its permittivity vanishes. We observe a change in the real part of the refractive index of 0.72 ± 0.025, corresponding to 170% of the linear refractive index. This change in refractive index is reversible with a recovery time of about 360 femtoseconds. Our results offer the possibility of designing material structures with large ultrafast nonlinearity for applications in nanophotonics.

Monolithic perovskite/silicon-heterojunction tandem solar cells processed at low temperature

Abstract: Tandem solar cells combining silicon and perovskite absorbers have the potential to outperform state-of-the-art high efficiency silicon single junction devices. However, the practical fabrication of monolithic silicon/perovskite tandem solar cells is challenging as material properties and processing requirements such as temperature restrict the device design. Here, we fabricate an 18% efficient monolithic tandem cell formed by a silicon heterojunction bottom- and a perovskite top-cell enabling a very high open circuit voltage of 1.78 V. The monolithic integration was realized via low temperature processing of the semitransparent perovskite sub-cell where an energetically aligned electron selective contact was fabricated by atomic layer deposition of tin oxide. The hole selective, transparent top contact was formed by a stack of the organic hole transport material spiro-OMeTAD, molybdenum oxide and sputtered indium tin oxide. The tandem cell design is currently limited by the photocurrent generated in the silicon bottom cell that is reduced due to reflectance losses. Based on optical modelling and first experiments, we show that these losses can be significantly reduced by combining optical optimization of the device architecture including light trapping approaches.

High-efficiency robust perovskite solar cells on ultrathin flexible substrates

Abstract: Wide applications of personal consumer electronics have triggered tremendous need for portable power sources featuring light-weight and mechanical flexibility. Perovskite solar cells offer a compelling combination of low-cost and high device performance. Here we demonstrate high-performance planar heterojunction perovskite solar cells constructed on highly flexible and ultrathin silver-mesh/conducting polymer substrates. The device performance is comparable to that of their counterparts on rigid glass/indium tin oxide substrates, reaching a power conversion efficiency of 14.0%, while the specific power (the ratio of power to device weight) reaches 1.96 kW kg(-1), given the fact that the device is constructed on a 57-μm-thick polyethylene terephthalate based substrate. The flexible device also demonstrates excellent robustness against mechanical deformation, retaining >95% of its original efficiency after 5,000 times fully bending. Our results confirmed that perovskite thin films are fully compatible with our flexible substrates, and are thus promising for future applications in flexible and bendable solar cells.

Metallic Nanowire-Based Transparent Electrodes for Next Generation Flexible Devices: a Review

Abstract: Transparent electrodes attract intense attention in many technological fields, including optoelectronic devices, transparent film heaters and electromagnetic applications. New generation transparent electrodes are expected to have three main physical properties: high electrical conductivity, high transparency and mechanical flexibility. The most efficient and widely used transparent conducting material is currently indium tin oxide (ITO). However the scarcity of indium associated with ITO's lack of flexibility and the relatively high manufacturing costs have a prompted search into alternative materials. With their outstanding physical properties, metallic nanowire (MNW)-based percolating networks appear to be one of the most promising alternatives to ITO. They also have several other advantages, such as solution-based processing, and are compatible with large area deposition techniques. Estimations of cost of the technology are lower, in particular thanks to the small quantities of nanomaterials needed to reach industrial performance criteria. The present review investigates recent progress on the main applications reported for MNW networks of any sort (silver, copper, gold, core-shell nanowires) and points out some of the most impressive outcomes. Insights into processing MNW into high-performance transparent conducting thin films are also discussed according to each specific application. Finally, strategies for improving both their stability and integration into real devices are presented.

Highly Stable Transparent Conductive Silver Grid/PEDOT:PSS Electrodes for Integrated Bifunctional Flexible Electrochromic Supercapacitors

Abstract: Silver grids are attractive for replacing indium tin oxide as flexible transparent conductors. This work aims to improve the electrochemical stability of silver-based transparent conductors. A silver grid/PEDOT:PSS hybrid film with high conductivity and excellent stability is successfully fabricated. Its functionality for flexible electrochromic applications is demonstrated by coating one layer of WO3 nanoparticles on the silver grid/PEDOT:PSS hybrid film. This hybrid structure presents a large optical modulation of 81.9% at 633 nm, fast switching, and high coloration efficiency (124.5 cm2 C−1). More importantly, an excellent electrochemical cycling stability (sustaining 79.1% of their initial transmittance modulation after 1000 cycles) and remarkable mechanical flexibility (optical modulation decay of only 7.5% after 1200 compressive bending cycles) is achieved. A novel smart supercapacitor is presented that functions as a regular energy-storage device and simultaneously monitors the level of stored energy by a rapid and reversible color variation even at high current charge/discharge conditions. The film sustains an optical modulation of 87.7% and a specific capacitance of 67.2% at 10 A g−1 compared to their initial value at a current density of 1 A g−1. The high-performance silver grid/PEDOT:PSS hybrid transparent films exhibit promising features for various emerging flexible electronics and optoelectronic devices.

Ultrafast switching of tunable infrared plasmons in indium tin oxide nanorod arrays with large absolute amplitude

Abstract: All-optical control of plasmons can enable optical switches with high speeds, small footprints and high on/off ratios. Here we demonstrate ultrafast plasmon modulation in the near-infrared (NIR) to mid-infrared (MIR) range by intraband pumping of indium tin oxide nanorod arrays (ITO-NRAs). We observe redshifts of localized surface plasmon resonances arising from a change of the plasma frequency of ITO, which is governed by the conduction band non-parabolicity. We generalize the plasma frequency for non-parabolic bands, quantitatively model the fluence-dependent plasma frequency shifts, and show that different from noble metals, the lower electron density in ITO enables a remarkable change of electron distributions, yielding a significant plasma frequency modulation and concomitant large transient bleaches and induced absorptions, which can be tuned spectrally by tailoring the ITO-NRA geometry. The low electron heat capacity explains the sub-picosecond kinetics that is much faster than noble metals. Our work demonstrates a new scheme to control infrared plasmons for optical switching, telecommunications and sensing. Ultrafast plasmon modulation has been realized in the near- to mid-infrared range by intraband pumping of indium tin oxide nanorod arrays.

Perovskite Photodetectors Operating in Both Narrowband and Broadband Regimes

Abstract: Photodetectors are designed, which operate in the broadband regime upon bottom illumination (from the indium tin oxide (ITO) side) and in the narrowband regime upon top illumination (from the air/perovskite side). The narrowband photodetectors show high external quantum efficiency of above 104 %. The operational spectrum of the photodetectors can also be tuned by adjusting the halide composition in the active material.

Fully Printed Halide Perovskite Light-Emitting Diodes with Silver Nanowire Electrodes

Abstract: Printed organometal halide perovskite light-emitting diodes (LEDs) are reported that have indium tin oxide (ITO) or carbon nanotubes (CNTs) as the transparent anode, a printed composite film consisting of methylammonium lead tribromide (Br-Pero) and poly(ethylene oxide) (PEO) as the emissive layer, and printed silver nanowires as the cathode. The fabrication can be carried out in ambient air without humidity control. The devices on ITO/glass have a low turn-on voltage of 2.6 V, a maximum luminance intensity of 21014 cd m(-2), and a maximum external quantum efficiency (EQE) of 1.1%, surpassing previous reported perovskite LEDs. The devices on CNTs/polymer were able to be strained to 5 mm radius of curvature without affecting device properties.

A Self‐Powered and Stable All‐Perovskite Photodetector–Solar Cell Nanosystem

Abstract: Hybrid organic–inorganic perovskites have attracted intensive interest as light absorbing materials in solid-state solar cells. Herein, we demonstrate a high-performance CH3NH3PbI3-based perovskite photodetector constructed on the flexible indium tin oxide (ITO) coated substrate even after 200 bending cycles. The as-fabricated devices show high responsivity, broad spectrum response from ultraviolet to whole visible light, long-term stability, and high on-off ratio. Particularly, atomic layer deposition technique was used to deposit the ultrathin Al2O3 film on devices, functioning as a protection layer to effectively enhance the stability and durability of perovskite photodetectors. The first all-perovskite self-powered nanosystem was successfully assembled by integrating a perovskite solar cell with a perovskite photodetector. Driven by the perovskite solar cell, the photodetector exhibits fast and stable response to illuminated light at a low working voltage less than 1.0 V. This stable integrated nanosystem has promising applications in which photodetectors can work in harsh environments without external power sources.

High-Efficiency Nanowire Solar Cells with Omnidirectionally Enhanced Absorption Due to Self-Aligned Indium–Tin–Oxide Mie Scatterers

Abstract: Photovoltaic cells based on arrays of semiconductor nanowires promise efficiencies comparable or even better than their planar counterparts with much less material. One reason for the high efficiencies is their large absorption cross section, but until recently the photocurrent has been limited to less than 70% of the theoretical maximum. Here we enhance the absorption in indium phosphide (InP) nanowire solar cells by employing broadband forward scattering of self-aligned nanoparticles on top of the transparent top contact layer. This results in a nanowire solar cell with a photovoltaic conversion efficiency of 17.8% and a short-circuit current of 29.3 mA/cm2 under 1 sun illumination, which is the highest reported so far for nanowire solar cells and among the highest reported for III–V solar cells. We also measure the angle-dependent photocurrent, using time-reversed Fourier microscopy, and demonstrate a broadband and omnidirectional absorption enhancement for unpolarized light up to 60° with a wavelength...

Phosphonic Acids for Interfacial Engineering of Transparent Conductive Oxides

Abstract: Transparent conducting oxides (TCOs), such as indium tin oxide and zinc oxide, play an important role as electrode materials in organic-semiconductor devices. The properties of the inorganic–organic interface—the offset between the TCO Fermi level and the relevant transport level, the extent to which the organic semiconductor can wet the oxide surface, and the influence of the surface on semiconductor morphology—significantly affect device performance. This review surveys the literature on TCO modification with phosphonic acids (PAs), which has increasingly been used to engineer these interfacial properties. The first part outlines the relevance of TCO surface modification to organic electronics, surveys methods for the synthesis of PAs, discusses the modes by which they can bind to TCO surfaces, and compares PAs to alternative organic surface modifiers. The next section discusses methods of PA monolayer deposition, the kinetics of monolayer formation, and structural evidence regarding molecular orientati...

PEDOT:PSS Films with Metallic Conductivity through a Treatment with Common Organic Solutions of Organic Salts and Their Application as a Transparent Electrode of Polymer Solar Cells.

Abstract: A transparent electrode is an indispensable component of optoelectronic devices, and there as been a search for substitutes of indium tin oxide (ITO) as the transparent electrode. Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conducting polymer that is very promising as the next generation of materials for the transparent electrode if it can obtain conductivity as high as that of ITO. Here, we report the treatment of PEDOT:PSS with organic solutions to significantly enhance its conductivity. Common organic solvents like dimethylformamide and γ-butyrolactone and common organic salts like methylammonium iodide and methylammonium bromide are used for the organic solutions. The conductivity of pristine PEDOT:PSS films is only ∼0.2 S/cm, and it can be increased to higher than 2100 S/cm. The conductivity enhancement is much more significant than control treatments of PEDOT:PSS films with neat organic solvents or aqueous solutions of the organic salts. The mechanism for the conductivi...

Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes

Abstract: Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening. Replacing indium tin oxide with graphene in organic light-emitting diodes is a promising approach to enhance the flexibility of displays and light sources. Here, the authors combine graphene, TiO2and low-index hole-injection layers to achieve high external quantum efficiency and good bendability.

50% Sn-Based Planar Perovskite Solar Cell with Power Conversion Efficiency up to 13.6%

Abstract: In the present work, a Pb-assisted two step method is successfully proposed to fabricate high-quality CH3NH3Sn0.5Pb0.5I3 (MASn0.5Pb0.5I3) perovskite film on the indium tin oxide (ITO) glass/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) substrate. The film shows regular crystalline grains with a flat and compact morphology as well as full coverage on the planar PEDOT:PSS substrate. Remarkably, corresponding devices ITO/PEDOT:PSS/MASn0.5Pb0.5I3/C60/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/Ag are fabricated with high reproducibility, achieving a high power conversion efficiency of 13.6%, which is, to the best of knowledge, the most efficient solar cell based on Sn-based perovskite.

Work Function Tuning of Reduced Graphene Oxide Thin Films

Abstract: Graphene oxide (GO) has shown great potential as a component in various devices due to its excellent solution processability and two-dimensional structure. However, the oxygenated form of graphene has a moderate charge-transport capability. The latter parameter may be enhanced through controlled deoxygenation of GO with subsequent tuning of its work function (WF). Various reduction approaches were employed to investigate the effect of the oxygen content on the work function of GO derivatives as thin films on an indium tin oxide substrate. Such films were reduced by stepwise thermal annealing in ultrahigh vacuum up to 650 °C, by chemical reduction with hydrazine, or by a combination of chemical and thermal reduction processes. The effect of the GO film thickness and the flake size on the WF was also investigated. UV photoelectron spectroscopy and X-ray photoelectron spectroscopy were used to correlate the WF of GO derivatives with their oxygen content. The results showed that the WF is strongly dependent o...

Simple hydrothermal synthesis of very-long and thin silver nanowires and their application in high quality transparent electrodes

Abstract: Solution-processed silver nanowire (AgNW) random mesh is a strong contender to commercial indium tin oxide (ITO); however, its performance is limited due to large contact resistance between nanowires and post-processing treatments. As an alternative, long nanowires can decrease the number of contact points and contact resistance. Here, a simple modified hydrothermal method for the synthesis of very-long silver nanowires (AgNWs) and their use in a high quality transparent conducting electrode without post-processing has been developed. Well dispersed very-long and thin silver nanowires are synthesized by using glucose as a reducing agent and silver chloride as a silver source. The lengths of the wires are in the range of 200 to 500 μm with an average diameter of 45–65 nm. To the best of our knowledge, this is the first report on long nanowires having a thin diameter with greater than 200 microns length. As compared to other transparent conductors and nanowire networks, this AgNW network shows a higher percolative figure of merit (FoM, Π) with low haze. A flexible touch screen using the AgNW network is also demonstrated which has shown good performance even on a bendable surface.

Rational wiring of photosystem II to hierarchical indium tin oxide electrodes using redox polymers

Abstract: Photosystem II (PSII) is a multi-subunit enzyme responsible for solar-driven water oxidation to release O2 and highly reducing electrons during photosynthesis. The study of PSII in protein film photoelectrochemistry sheds light into its biological function and provides a blueprint for artificial water-splitting systems. However, the integration of macromolecules, such as PSII, into hybrid bio-electrodes is often plagued by poor electrical wiring between the protein guest and the material host. Here, we report a new benchmark PSII–electrode system that combines the efficient wiring afforded by redox-active polymers with the high loading provided by hierarchically-structured inverse opal indium tin oxide (IO-ITO) electrodes. Compared to flat electrodes, the hierarchical IO-ITO electrodes enabled up to an approximately 50-fold increase in the immobilisation of an Os complex-modified and a phenothiazine-modified polymer. When the Os complex-modified polymer is co-adsorbed with PSII on the hierarchical electrodes, photocurrent densities of up to ∼410 μA cm−2 at 0.5 V vs. SHE were observed in the absence of diffusional mediators, demonstrating a substantially improved wiring of PSII to the IO-ITO electrode with the redox polymer. The high photocurrent density allowed for the quantification of O2 evolution, and a Faradaic efficiency of 85 ± 9% was measured. As such, we have demonstrated a high performing and fully integrated host–guest system with excellent electronic wiring and loading capacity. This assembly strategy may form the basis of all-integrated electrode designs for a wide range of biological and synthetic catalysts.

High-Performance Polymer Solar Cells with PCE of 10.42% via Al-Doped ZnO Cathode Interlayer.

Abstract: High-performance polymer solar cells incorporating a low-temperature-processed aluminum-doped zinc oxide (AZO) cathode interlayer are constructed with power conversion efficiency (PCE) of 10.42% based on PTB7-Th:PC71 BM blends (insensitive to the AZO thickness). Moreover, flexible devices on poly(ethylene terephthalate)/indium tin oxide substrates with PCE of 8.93% are also obtained, and welldistributed efficiency and good device stability are demonstrated as well.

Solution-Processed CuS NPs as an Inorganic Hole-Selective Contact Material for Inverted Planar Perovskite Solar Cells

Abstract: Organic–inorganic hybrid perovskite solar cells (PSCs) have drawn worldwide intense research in recent years. Herein, we have first applied another p-type inorganic hole-selective contact material, CuS nanoparticles (CuS NPs), in an inverted planar heterojunction (PHJ) perovskite solar cell. The CuS NP-modification of indium tin oxide (ITO) has successfully tuned the surface work function from 4.9 to 5.1 eV but not affect the surface roughness and transmittance, which can effectively reduce the interfacial carrier injection barrier and facilitate high hole extraction efficiency between the perovskite and ITO layers. After optimization, the maximum power conversion efficiency (PCE) has been over 16% with low J–V hysteresis and excellent stability. Therefore, the low-cost solution-processed and stable CuS NPs would be an alternative interfacial modification material for industrial production in perovskite solar cells.

Morphology Engineering for High-Performance and Multicolored Perovskite Light-Emitting Diodes with Simple Device Structures.

Abstract: The film morphology is extremely significant for solution processed perovskite devices. Through fine morphology engineering without using any additives or further posttreatments, a full-coverage and high quantum yield perovskite film has been achieved based on one-step spin-coating method. The morphologies and film characteristics of MAPbBr3 with different MABr:PbBr2 starting material ratios are in-depth investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, photoluminescence, and time resolved photoluminescence. High performance organometal halide perovskite light-emitting didoes (PeLEDs) based on simple device structure of indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/perovskite/TPBi/Ca/Al are demonstrated. The green PeLED based on MAPbBr3 shows a maximum luminance of 8794 cd m−2 (at 7.3 V) and maximum current efficiency of 5.1 cd A−1 (at 5.1 V). Furthermore, a class of hybrid PeLEDs by adjusting the halide ratios of methylammonium lead halide (MAPbX3, where X is Cl, Br, or I) are also demonstrated at room temperature. These mix-halogenated PeLEDs show bright luminance (above 100 cd m−2) with narrow and clean emission bands over the wide color gamut.

Copper Nanowires and Their Applications for Flexible, Transparent Conducting Films: A Review.

Abstract: Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and mechanical properties. In this study, we report a summary of recent advances in research on Cu NWs, covering the optoelectronic properties, synthesis routes, deposition methods to fabricate flexible transparent conducting films, and their potential applications. This review also examines the approaches on protecting Cu NWs from oxidation in air environments.

Graphene and Graphene-like Molecules: Prospects in Solar Cells.

Abstract: Graphene is constantly hyped as a game-changer for flexible transparent displays. However, to date, no solar cell fabricated on graphene electrodes has out-performed indium tin oxide in power conversion efficiency (PCE). This Perspective covers the enabling roles that graphene can play in solar cells because of its unique properties. Compared to transparent and conducting metal oxides, graphene may not have competitive advantages in terms of its electrical conductivity. The unique strength of graphene lies in its ability to perform various enabling roles in solar cell architectures, leading to overall improvement in PCE. Graphene can serve as an ultrathin and transparent diffusion barrier in solar cell contacts, as an intermediate layer in tandem solar cells, as an electron acceptor, etc. Inspired by the properties of graphene, chemists are also designing graphene-like molecules in which the topology of π-electron array, donor–acceptor structures, and conformation can be tuned to offer a new class of ligh...

An antireflection transparent conductor with ultralow optical loss (<2 %) and electrical resistance (<6 Ω sq-1).

Abstract: Transparent conductors are essential in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and solar cells. Here we demonstrate a transparent conductor with optical loss of ∼1.6%, that is, even lower than that of single-layer graphene (2.3%), and transmission higher than 98% over the visible wavelength range. This was possible by an optimized antireflection design consisting in applying Al-doped ZnO and TiO2 layers with precise thicknesses to a highly conductive Ag ultrathin film. The proposed multilayer structure also possesses a low electrical resistance (5.75 Ω sq−1), a figure of merit four times larger than that of indium tin oxide, the most widely used transparent conductor today, and, contrary to it, is mechanically flexible and room temperature deposited. To assess the application potentials, transparent shielding of radiofrequency and microwave interference signals with ∼30 dB attenuation up to 18 GHz was achieved. Transparent conductors are fundamental for optoelectronics. Using the transfer matrix method to optimise a multistructure of anti-reflection coatings containing an ultrathin metal film, Maniyaraet al. achieve the highest transmittance of an antireflection transparent conductor combined with low resistance.

In Situ Rapid Formation of a Nickel–Iron-Based Electrocatalyst for Water Oxidation

Abstract: If an oxygen evolution reaction (OER) catalyst is expected to be more durable, especially under conditions of thin-layer catalysts or strong gas evolution, it will ideally function in a self-repair mode. In earlier studies, the electrochemical fabrications of Ni–Fe oxide catalysts were exclusively carried out by cathodic reduction of Ni(II) and Fe(III,II) in an individual solution that is different from the alkaline media commonly used for the OER. The procedure does not suggest that the dissolution/corrosion of the film catalysts could be countered by continual catalyst formation during the OER. Herein, we report a highly active NiFeOx catalyst by in situ rapid (3–15 min) anodic deposition of Ni(II) and Fe(III,II) in concentrated carbonate solution. At a transparent indium tin oxide (ITO) electrode, the conformal deposition of NiFeOx (7–11-atom layer) results in a very low optical loss (5–8%) with activity comparable to that of other planar NiFeOx films. Extension to a 3D nickel foam produces a hierarchi...