Optical charge carrier generation in a conjugated polymer

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.

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%.

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

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.

The facile deposition of para-substituted aryl films onto indium-tin oxide (ITO) electrodes by the electrochemical reduction of aryl diazonium salts in acetonitrile is reported. For the deposition conditions used in this report, the aryl film thicknesses are on the order of 1-6 nm, suggesting a multilayer structure. Regardless of the functional group on the aryl diazonium cation, (NO(2), CO(2)H, or fluorene) the electrodeposition behavior onto ITO electrodes is similar to that seen on other electrode materials. XPS and UV-vis data support the introduction of organic functional surface groups to ITO. The blocking behavior of the aryl films on ITO toward the Ru(NH(3))(6)(3+/2+) redox couple is in agreement with electron transfer through conjugated organic layers. The facile preparation of patterned aryl films with regular-spaced 700 nm voids on ITO is also described. Atomic force microscopy and scanning surface potential microscopy on patterned NO(2) aryl films are used to assess the molecular structure and orientation. A 100 mV decrease in the contact potential over NO(2) aryl films relative to bare ITO suggests that the aryl films are loosely structured as deposited with the NO(2) groups oriented at a small angle away from the ITO surface.

We have measured the photocurrent action spectra of the conjugated polymers poly[2-methoxy, 5 ethyl (2\ensuremath{'} hexyloxy) paraphenylenevinylene] (MEH-PPV) and poly(phenylenevinylene) (PPV) in sandwich cells between indium tin oxide (ITO) and aluminum electrodes. Under forward bias and illumination through ITO, the photocurrent spectrum is broad and has a maximum at high energy, where the absorption coefficient is greatest (the symbatic response). Under reverse bias and illumination through ITO, the photocurrent spectrum consists of a very narrow peak (the full width at half maximum is 0.1 eV), located in the low-energy tail of the absorption profile (the antibatic response). Several established models attempt to explain this behavior and to relate the photocurrent action spectrum to the absorption coefficient, considering penetration depth of the light and diffusion of excitons or directly photogenerated charges. At a qualitative level many of these seem to provide an adequate description. In this paper, we undertake a quantitative examination of these models and we find that none of them can reproduce the very narrow antibatic response that we observe in both MEH-PPV and PPV. Upon exposure to air, we observe an enhancement of the photocurrent by a much greater factor than the dark current, from which we conclude that charge generation is mediated by exciton dissociation. As the temperature decreases we observe a progressive redshift of the absorption edge, although the photocurrent onset undergoes a much smaller redshift. We therefore conclude that the narrow antibatic peak is due to a specific enhancement of dissociation upon excitation at low energy. We propose that the particularly sharp onset of photocurrent at low energy may be due to enhanced intermolecular charge separation within crystallite grains between those neighboring conjugated segments that are more extended and more planar.

AFM, CLSM and EIS characterization of the immobilization of antibodies on indium–tin oxide electrode and their capture of Legionella pneumophila

We report a self-powered photodetector based on the vertical p-MoTe2/n-MoS2 van der Waals heterostructure with indium tin oxide (ITO) electrodes, that exhibits an ultra-fast response of ∼172 μs and high responsivity (R) up to 146 mA W−1 in the wavelengths from 450 and 980 nm. An unique bidirectional photocurrent response was observed, varying from visible light to near infrared light, which could be attributed to the band alignments of type II heterostructure and ITO electrodes. This MoTe2/MoS2 heterostructure photodetector with ITO electrodes provides more opportunities for future nanoscale electronic and optoelectronic applications.

Hemoglobin (Hb) was chemically modified with poly(ethylene oxide) (PEO) to prepare PEO‐Hb. This PEO‐Hb was cast onto the ITO (Indium Tin Oxide) electrode, and the modified electrode was then soaked in PEO oligomer solution containing 0.2 m KCI. PEO‐Hb was electrochemically reduced by applying a negative potential (ranging from −0.5 to −1.2 V vs. Ag). Electron transfer between adjacent PEO‐Hbs in the cast layer was considered to be slow. Higher salt concentration and more negative potential gave an effective reduction of PEO‐Hb in PEO oligomers. Re‐oxidation of the reduced PEO‐Hb was also carried out by giving positive potential. This redox reaction was confirmed as reversible by potential polarity charge. A similar redox reaction was carried out in dry poly(oligo(oxyethylene) methacrylate) containing KCl. Polymer electrolytes were revealed to be effective polymer solvents for the redox reaction of PEO‐modified hemoglobin cast on the ITO electrode.

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.

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

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.