Ultra-sensitive self-powered photodetector based on vertical MoTe2/MoS2 heterostructure

We report a simple solution-based approach to form ordered patterns of an indium tin oxide (ITO) electrode and underlying reasons for the improvement in power conversion efficiency (PCE) of organic solar cells (OSCs) built on the nanostructured ITO electrode. The patterning of ITO was achieved by using nanospheres as the template to erode ITO by wet chemical etching. Using a textured ITO anode for poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61-butyric acid methylester (PCBM) (P3HT:PCBM) OSCs enhanced PCE by 15% with respect to the non-patterned ITO anode. The improvement is mostly attributed to the morphological and interfacial changes stemming from the textured ITO electrode as well as enhanced light absorption due to the optimal morphology and refractive index change of patterned ITO. With its simplicity and time-saving, this method of fabricating a unique pattern of ITO electrodes can be widely applicable to a variety of large-area thin film solar cells.

Enhancement of the light output of GaN-based light-emitting diodes with surface-patterned ITO electrodes by maskless wet-etching

A promising nitrite sensor based on one‐dimensional polyoxometalate hybrid nanofibers was prepared and developed by electrospinning of a mixture of poly(vinyl alcohol) and α‐K6[P2W18O62]⋅14H2O (P2W18) onto the surface of an indium tin oxide (ITO) electrode. After thermal crosslinking, the P2W18 hybrid nanofibers are insoluble in aqueous solutions even after a period of 24 hours, which ensures the electrochemical stability of the P2W18 hybrid nanofiber‐modified ITO electrode. The cyclic voltammetry results have demonstrated that the P2W18 hybrid nanofiber‐modified ITO electrode exhibits excellent electrocatalytic activity toward the reduction of nitrite in acidic solutions. Additionally, long‐term stability and reproducibility have been observed.

The avoiding of the hole transport layer (HTL) by an UV/ozone treatment of the indium tin oxide (ITO) electrode was successfully tested on the P3HT:PC61BM and PBDTTT‐CF:PC71BM organic solar cells with plasmonic gold nanoparticles and gold nanorods spincoated on ITO, respectively. Reference device on bare UV‐ozone treated ITO and the one with HTL were also prepared for comparison. It was found that the UV/ozone treatment of the bare ITO and plasmon‐enhanced ITO electrode allowed an effective alignment of the electrode work function with the polymer in the active layer at the saturated values of 5.5 eV and 5.6 eV, respectively. This result is well explained by the integer charge transfer model. The power conversion efficiency (PCE) of the device on bare UV/ozone treated ITO was comparable to that of the conventional device with HTL. Application of two types of 30 nm gold nanoparticles and 40 nm long gold nanorods on ITO before the subsequent UV/ozone treatment improved the PCE by up to 20% and 10%, respectively. These results suggest feasibility of a simple and cost‐effective preparation of OSCs.

Spin-coated Au-nanohole arrays engineered by nanosphere lithography for a Staphylococcus aureus 16S rRNA electrochemical sensor

Ferric ion (Fe3+) contamination in water sources poses significant risks, making reliable detection technologies essential. In this study, electrochemical sensors were developed by spray-coating Graphene quantum dots (GQDs) on indium tin oxide (ITO) electrodes to enhance Fe3+ detection in aqueous systems. The performance of Assembly GQDs and GQDs on ITO electrodes was compared, and the electrochemical sensing of Fe3+ was investigated. GC-358 exhibited a 3D structure with aggregated particles and high electroconductivity, while CLS-3 showed a broad absorption peak around 300 nm and green photoluminescence at 505 nm due to carboxyl groups. Cyclic voltammetry showed the highest current response for CLS-3 at 4 mg with Nafion, reaching 1.32 × 10-6 A at 0.04 V, due to increased film thickness and Nafion enhancement. In comparison, GC-358 at 4 mg with Nafion exhibited a current of 6.29 × 10⁻⁷ A at 0.58 V, with slower charge transfer rates. Nafion improved electron transfer for both electrodes. GC-358 at 4 mg with Nafion provided the best Fe3+ detection performance, attributed to its stable sp2 hybridization and sheet-like morphology. CLS-3 at 4 mg with Nafion showed similar performance but with faster charge transfer and less efficient electron transfer due to its dot-like morphology. The sensor performance showed that ITO had the highest (Limit of detection) LOD of 1041.08 mg/L and limit of quantification (LOQ) of 3470.27 mg/L, with a low sensitivity of 6.85 × 10-9 AL/mg. GC-358/ITO at 4 mg with Nafion had a lower LOD of 0.53 mg/L, LOQ of 1.77 mg/L, sensitivity of 1.41 × 10-7 AL/mg, and high R2 of 0.9802. CLS-3/ITO at 4 mg with Nafion exhibited even higher sensitivity of 2.45 × 10-7 AL/mg, lower LOD of 1.16 mg/L, and excellent precision with R2 of 0.9905 and relative standard deviation (RSD) of 17.59%.

In this study, chemical treatment (CT; oxidation–reduction method) and physical treatment (HP; hot-pressing methods) were applied to improve the performance of silver nanowire (AgNW)-derived electrodes on a glass or flexible polyethylene terephthalate (PET) substrate. The four-point probe method, UV-Vis spectroscopy and scanning electron microscopy (SEM) were used to measure the properties of AgNW electrodes and compare them with those of indium tin oxide (ITO) electrodes for exploring the possibility of using CT- and HP-based AgNW electrodes for polymer solar cell (PSC) applications. Using the CT or HP method, the sheet resistance of electrodes decreased to lower than 40 Ω sq−1 with an average high transmittance of more than 80%. Furthermore, HP reduced the surface roughness of AgNWs, which solved the inter-electrode short circuiting problem for devices. We studied the performance of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) and zinc oxide-based PSC devices. The power conversion efficiency of HP-AgNW-derived poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl] (PTB7-Th):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) devices was 7.83%, which was slightly lower than the performance of the device using ITO (8.03%) as a substrate. After a bend test (100 times) at a 2-cm curvature radius, the efficiency of AgNW/PET-derived PSCs was more than 70%. The performance of PSCs made with AgNWs and ITO electrodes is comparable, but the cost of using AgNWs for electrodes is much lower; therefore, HP-derived AgNWs demonstrate great potential for optoelectronic applications.

An indium tin oxide (ITO) electrode coated with monolayer TiO2/[Ru(phen)2(dC18bpy)]2+ (phen = 1,10-phenanthroline, dC18bpy = 4,4′-dioctadecyl-2,2′-bipyridyl) hybrid film (denoted as ITO/TiO2-Ru) has been prepared using the modified Langmuir-Blodgett (LB) method, and the electrocatalytic oxidation of mononucleotide of guanosine 5′-monophosphate (GMP) on an ITO/TiO2-Ru electrode after Pd-photodeposition (denoted as ITO/TiO2-Ru/Pd) has been studied. Atomic force microscopy reveals that the single-layered hybrid film of TiO2 nanosheets/[Ru(phen)2(dC18bpy)]2+ is closely packed at a surface pressure of 25 mN m−1 and has a thickness of (3.20 ± 0.5) nm. X-ray photoelectron spectra show the formation of Pd nanoparticles on the surface of hybrid film with radii of 20–200 nm by the reduction of [Pd(NH3)4]2+ under light irradiation. When it is applied to oxidize GMP, a larger catalytic oxidative current is achieved on the ITO/TiO2-Ru/Pd electrode at the external potential above 700 mV (vs. Ag|AgCl|KCl) in comparison with the naked ITO electrode and ITO/TiO2-Ru electrode. Such a result indicates that the Pd nanoparticles are able to hamper the combination of electron hole pairs and reduce the counterwork of insulating long alkyl chains of amphiphilic Ru(II) complexes, and thus develops the electron transfer efficiency and produces the enhanced redox current.

An improved method for connecting flexible printed circuits and indium tin oxide (ITO) electrodes is proposed in this paper. The adhesives used were composed of a thermosetting resin and a thermoplastic resin. The test sample consisted of a polyimide base flexible printed circuit, (FPC). Non-conductive film (NCF) was pre-laminated on an ITO-glass and the test sample was then thermally bonded to the glass. The contact resistance between the ITO-glass and FPC was measured by a 4-probe method. A Cu wiring on the FPC was chemically etched, followed by selective electroless Ni–P deposition using hydrazine and sodium hypophosphite as reducing agents; Au film was then plated onto it. Since this method does not create extraneous deposition, it is one of the most promising candidates for future fine connection manufacturing processes. With lines and spaces of 75 μm and 75 μm, insulation resistance of 1 × 108 Ω remained constant at 60 °C, 90 %RH, 30 V for 60 hours. Various FPCs with different line and space combinations have been investigated by the same method. The lines and spaces of 15 μm and 25 μm, 20 μm and 20 μm, and 25 μm and 15 μm show contact resistance of 2.02 Ω, 1.26 Ω and 0.844 Ω, respectively. Therefore, this method is intrinsically suitable for fine pitch FPCs with high reliability.

A simple and label-free electrochemical DNA hybridization sensor was developed based on a poly(thionine)/gold nanoparticle composite-modified indium tin oxide (PTH/GNPs/ITO) electrode. The PTH/GNPs/ITO electrode was prepared by the electrodeposition of GNPs on ITO followed by the electropolymerization of thionine (TH). Probe DNA (pDNA) was immobilized on this substrate via covalent linkage between the -NH2 group of PTH and the PO43− group at the 5′ end of pDNA. The immobilized single-strand pDNA increased the stiffness of the PTH film and decreased the PTH oxidation current, whereas the current was reduced to a greater extent after the formation of double-strand DNA by the hybridization of target complementary DNA (cDNA). The pDNA/PTH/GNPs/ITO sensor exhibited excellent stability, and selectivity to discriminate DNA base pair mismatches. The semi-log plot of the [cDNA] vs. oxidation current of PTH was linear in the concentration range of 1 μM − 1 fM with the detection limit (S/N = 3) and sensitivity of ca. 0.3 fM and ca. 2.0 μA·cm−2·fM−1, respectively.

Photosystem II (PSII) offers a biological and sustainable route of photochemical water oxidation to O2 and can provide protons and electrons for the generation of solar fuels, such as H2. We present a rational strategy to electrostatically improve the orientation of PSII from a thermophilic cyanobacterium, Thermosynechococcus elongatus, on a nanostructured indium tin oxide (ITO) electrode and to covalently immobilize PSII on the electrode. The ITO electrode was modified with a self-assembled monolayer (SAM) of phosphonic acid ITO linkers with a dangling carboxylate moiety. The negatively charged carboxylate attracts the positive dipole on the electron acceptor side of PSII via Coulomb interactions. Covalent attachment of PSII in its electrostatically improved orientation to the SAM-modified ITO electrode was accomplished via an amide bond to further enhance red-light-driven, direct electron transfer and stability of the PSII hybrid photoelectrode.

Molecular electronics exhibiting resistive-switching memory features hold great promise for the next generation of digital technology. In this work, electrosynthesis of ruthenium polypyridyl nanoscale oligomeric films is demonstrated on an indium tin oxide (ITO) electrode followed by an ITO top contact deposition yielding large-scale (junction area = 0.7 × 0.7 cm2) two terminal molecular junctions. The molecular junctions exhibit non-volatile resistive switching at a relatively lower operational voltage, ±1V, high ON/OFF electrical current ratio (≈103), low-energy consumption (SET/RESET = 27.94/14400 nJ), good cyclic stability (>300 cycles), and switching speed (SET/RESET = 25ms/20ms). A computational study suggests that accessible frontier molecular orbitals of metal-complex to the Fermi level of ITO electrodes facilitate charge transport at a relatively lower bias followed by a filamentformation. An extensive analysis is performed of the performance of binary neural networks exploiting the current-voltage features of the devices as binary synaptic weights and exploring their potential for neuromorphic logic-in-memory implementation of IMPLICATION (IMPLY) operation which can realize universal gates. The comprehensive analysis indicates that the proposed redox-active complex-based memory device may be a promising candidate for high-density data storage, energy-efficient implementation of neuromorphic networks with software-level accuracy, and logic-in-memory implementations.

Enhance external quantum efficiency of organic light-emitting devices using thin transparent electrodes

The performance of organic solar cells (OSCs), particularly flexible semi-transparent OSCs (ST-OSCs), is often limited by the use of indium tin oxide (ITO) electrodes, which are prone to cracking under bending and thus compromise device performance. This study introduces a novel silver mesh electrode (Ag-mesh) as a substitute for ITO in ST-OSCs. The Ag-mesh electrodes demonstrated optimal performance at a thermal imprinting temperature of 130 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C, with minimal line breakage and preserved optoelectronic properties. Compared to ITO electrodes, ST-OSCs with Ag-mesh electrodes showed superior mechanical stability, retaining over 90% of their initial performance after 1000 bending cycles, and an impressive retention of nearly 87% of their initial power conversion efficiency (PCE). The devices based on Ag-mesh electrodes also exhibited higher fill factor (FF) and better light response, aligning with higher conductivity and transmittance of the Ag-mesh electrodes. This research offers a significant contribution to the field by providing a durable and efficient alternative to ITO electrodes in flexible ST-OSCs. The Ag-mesh electrodes not only match but exceed the performance of ITO electrodes in terms of efficiency and stability, marking a substantial step forward in the development of flexible and semi-transparent solar cell technology.

The next generation of optoelectronic devices requires transparent conductive electrodes to be flexible, cheap, and compatible with large scale manufacturing processes. Indium Tin Oxide (ITO) electrodes are often used due to their superior transparency and conductance, however they are brittle, expensive and their fabrication requires vacuum conditions which restrict scale-up. One possible alternative to the traditional ITO electrode is the metal nanowire mesh (MNWM) electrode, which is transparent, conductive, flexible and easy to produce. In this work we present the preparation and characterization of a simple organic light emitting diode (OLED) device based on a transparent electrode made of ultrathin MNWM and a comparison to an ITO based device. We have found that MNWM electrodes offer a suitable alternative to ITO electrodes in OLED devices. We have also found that the failure rate for devices due to short circuits between the top and bottom electrodes was smaller in MNWM based devices compared to ITO based devices since the MNWM devices could be repaired to present normal OLED behavior by selectively burning the nanowires forming the short. The ability to “heal” organic devices presents an important advantage and also allows for future uses in applications such as roll to roll printing.