Ultra‐thin (002)‐oriented Al‐doped zinc oxide transparent electrode grown on oxygen‐controlled homo‐seed layer

Highly (002)‐oriented Al‐doped zinc oxide (AZO) thin films with the thickness of less than 200 nm have been deposited on an oxygen‐controlled homo‐seed layer at 200 °C by DC magnetron sputtering. With the homo‐seed layer being employed, the full‐width at half maximum (FWHM) of the (002) diffraction peak for the AZO ultra‐thin films decreased from 0.33° to 0.22°, and, the corresponding average grain size increased from 26.8 nm to 43.0 nm. The XRD rocking curves revealed that the AZO ultra‐thin film grown on the seed layer deposited in atmosphere of O₂/Ar of 0.09 exhibited the most excellent structural order. The AZO ultra‐thin film with homo‐seed layer reached a resistivity of 4.2 × 10^–4 Ω cm, carrier concentration of 5.2 × 10²⁰ cm^–3 and mobility of 28.8 cm² V^–1 s^–1. The average transmittance of the AZO ultra‐thin film with homo‐seed layer reached 85.4% in the range of 380–780 nm including the substrate. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transparent p‐NiO/n‐ZnO diodes used in circuit rectifiers

We report on the fabrication of a transparent photostable cell circuit composed of drive and resistor diodes which are face‐to‐face connected to each other with different device area. The diodes consisted of e‐beam evaporated p‐NiO on sputter‐deposited n‐ZnO for p/n diode formation on indium‐tin‐oxide glass. Our transparent diodes show photostable rectifying behavior, about 10³ on/off current ratio and even dynamic rectification at a maximum frequency of 100 Hz AC input signal in ambient light. The noticeable photo‐responsivity of the circuit was obtained only under ultraviolet (UV) light. We conclude that our transparent diode circuit is promising in enriching the field of transparent device electronics. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

One decade of fully transparent oxide thin‐film transistors: fabrication,performance and stability

We review the history of fully transparent oxide thin‐film transistors. Their performance and stability increased during the past ten years of their existence, thus enabling the design of novel applications in transparent electronics. However, certain disadvantages of the well established leading technology of metal–insulator–semiconductor field‐effect transistors (MISFETs), adapted from the silicon‐based complementary metal–oxide–semiconductor (CMOS) and thin‐film transistor technology, may be overcome by alternative transistor designs like metal–semiconductor field‐effect transistors (MESFETs). We compare the stability of published transparent MISFET with our transparent MESFET (TMESFET) technology against bias stress, towards illumination, at elevated temperatures and long‐term stability.

     

ITO‐free top emitting organic light emitting diodes with enhanced light out‐coupling

Bottom emitting organic light emitting diodes (OLEDs) can suffer from lower external quantum efficiencies (EQE) due to inefficient out‐coupling of the generated light. Herein, it is demonstrated that the current efficiency and EQE of red, yellow, and blue fluorescent single layer polymer OLEDs is significantly enhanced when a MoO_x(5 nm)/Ag(10 nm)/MoO_x(40 nm) stack is used as the transparent anode in a top emitting OLED structure. A maximum current efficiency and EQE of 21.2 cd/A and 6.7%, respectively, was achieved for a yellow OLED, while a blue OLED achieved a maximum of 16.5 cd/A and 10.1%, respectively. The increase in light out‐coupling from the top‐emitting OLEDs led to increase in efficiency by a factor of up to 2.2 relative to the optimised bottom emitting devices, which is the best out‐coupling reported using solution processed polymers in a simple architecture and a significant step forward for their use in large area lighting and displays.     

Very thin,highly‐conductive ZnO:Al front electrode on textured glass as substrate for thin‐film silicon solar cells

A very thin (250 nm), highly conductive (annealed), non‐texturized DC‐sputtered aluminum‐doped zinc oxide layer (ZnO:Al) deposited on a textured glass is used as substrate for thin‐film silicon solar cells. Compared to the classical approach, where wet‐chemically texturized ZnO:Al on planar glass is used, this approach allows a reduction in the as‐deposited ZnO:Al thickness of almost 70% while at the same time, thanks to the good light trapping capability of the glass texture the efficiency of the cells was maintained at the high level of 10.9%.

     

Nanosphere lithography with variable deposition angle for the production of one‐directional transparent conductors

The production of high quality and cheap transparent electrodes is a fundamental step for a variety of optoelectronic devices. We present a method for the production of transparent conducting films optimised for electrical conduction in one direction. The deposition of a metal film through a perfectly aligned nanosphere‐lithography mask at variable incidence angle gave origin to parallel nanowires with thin interconnections. This structure showed excellent conductivity in one direction and high optical transparency.

Glass substrates under the crystalline areas of the polystyrene‐nanospheres mask.     

Plasmonic refraction‐induced ultrahigh transparency of highly conducting metallic networks

We demonstrate a high optoelectronic performance and application potential of our random network, with subwavelength diameter, ultralong, and high‐quality silver nanowires, stabilized on a substrate with a UV binder. Our networks show very good optoelectronic properties, with the single best figure of merit of ∼1686, and excellent stability under harsh mechanical strain, as well as thermal, and chemical challenge. Our network transparency strongly exceeds the simple shading limit. We show that this transmission enhancement is due to plasmonic refraction, which in an effective medium picture involves localized plasmons, and identify the inhomogeneous broadening as the key factor in promoting this mechanism. Such networks could become a basis for a next generation of ultrahigh‐performance transparent conductors.

     

Light trapping for a‐Si:H/µc‐Si:H tandem solar cells using direct pulsed laser interference texturing

We present a‐Si:H/µc‐Si:H tandem solar cells on laser textured ZnO:Al front contact layers. Direct pulsed laser interference patterning (DLIP) was used for writing arrays of one‐dimensional micro gratings of submicron period into ZnO:Al films. The laser texture provides good light trapping which is indicated by an increase in short‐circuit current density of 20% of the bottom cell limited device compared to cells on planar ZnO:Al. The open‐circuit voltage of the cells on laser textured ZnO:Al is almost the same as for cells on planar substrates, indicating excellent growth conditions for amorphous and microcrystalline silicon on the U‐shaped grating grooves. DLIP is a simple, single step and industrially applicable method for large area periodic texturing of ZnO:Al thin films. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Raman spectroscopic investigation of lanthana‐doped neodymium‐yttria transparent ceramics

Transparent ceramics of the formula (Nd_0.01La_xY_0.99−x)₂O₃ (x = 0, 0.05, 0.10) were made with nanopowders and sintered in H₂ atmosphere. The Raman spectra of Ln₂O₃ (Ln = Y, La, Nd) powders and (Nd_0.01La_xY_0.99−x)₂O₃ ceramics were investigated. The results show that both La₂O₃ and Nd₂O₃ powders are of hexagonal structure, and all (Nd_0.01La_xY_0.99−x)₂O₃ ceramics exhibit the same cubic Y₂O₃ crystal structure. Their lattice parameters were refined by the Rietveld method. The full‐widths at half‐maximum of Raman peaks increase with the increase in La₂O₃ content in transparent (Nd_0.01Y_0.99)₂O₃ ceramics, while their intensities decrease. At the same time, All Raman peaks shift to lower wavenumbers, and the phonon energy is slightly reduced. Copyright © 2010 John Wiley & Sons, Ltd.     

Spectroscopic characterization of Yb:Sc₂O₃ transparent ceramics

Yb:Sc2O3 transparent ceramics are fabricated by a conventional ceramic process and sintering in H2 atmosphere. The room-temperature spectroscopic properties are investigated, and the Raman spectrum shows an obvious vibration characteristic band centred at 415 cm 1 . There are three broad absorption bands around 891, 937, and 971 nm, respectively. The strongest emission peak is centred at 1.04 μm with a broad bandwidth (11 nm) and an emission cross-section of 1.8×10 20 cm 2 . The gain coefficient implies a possible laser ability in a range from 990 nm to 1425 nm. The energy-level structure shows that Yb:Sc 2 O 3 ceramics have large Stark splitting at the ground state level due to their strong crystal field. All the results show that Yb:Sc2O3 transparent ceramics are a promising material for short pulse lasers.     

Transparent and flexible field emission display device based on single‐walled carbon nanotubes

A fully transparent and flexible field emission device (FED) has been demonstrated. Single‐walled carbon nanotubes (SWCNTs) coated on arylite substrate were used as electron emitters for the FED and a novel metavanadate phosphor coated on the SWCNTs/arylite film was used as transparent and flexible screen. The SWCNTs/arylite based emitters and the SWCNTs/arylite/metal‐vanadate‐based phosphor showed a transmittance value of 92.6% and 54%, respectively. The assembled device also showed satisfactory transparency and flexibility as well as producing significant current. Metavanadate phosphor is considered to be an excellent candidate due to its superior luminescence properties and easy fabrication onto transparent and flexible conductive substrate at room temperature while retaining reasonable transparency of the substrate. Thus, its transparency and flexibility will open the door to next‐generation FEDs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transparent and Superamphiphobic Surfaces from One‐Step Spray Coating of Stringed Silica Nanoparticle/Sol Solutions

Transparent and superamphiphobic coatings that repel both water and low‐surface‐tension oil offer energy and environmental benefits to building windows, solar cell panels, electronic displays, and other optical equipment. Here, we developed a solution consisting of stringed amphiphilic silica nanoparticles (NPs) and an amphiphilic sol, which could be spray coated onto a variety of planar and curved substrates in one step. High transparency, water/oil contact angles greater than 150° and roll‐off angles less than 10° were demonstrated. The stringed NPs formed a fractal‐like nanoporous network, while the sol acted as a surface modifier and binder to enhance the coating robustness against heating (up to 400 °C), water jetting, and sand abrasion.     

Wide band gap and p‐type conductive Cu–Nb–O films

Cu–Nb–O films with a thickness of ca. 150 nm were prepared on borosilicate glass substrates using CuNbO₃ ceramic target at substrate temperature of 500 °C by pulsed laser deposition. The X‐ray diffraction patterns showed that the Cu–Nb–O films were amorphous or an aggregation of fine crystals. The post‐annealed film at 300 °C in N₂ gas showed 80% transmission in visible light (band gap = 2.6 eV) and high p‐type conductivity of 21 S cm^–1. The Cu–Nb–O film with a thickness of 100 nm, fabricated from the target with a composition of Cu/Nb = 0.9, showed the highest p‐type conductivity of 116 S cm^–1. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Conformational analysis of N‐phenyl‐ and N‐trifyl‐4,4‐dimethyl‐4‐silathiane 1‐sulfimides

N‐Substituted 4,4‐dimethyl‐4‐silathiane 1‐sulfimides [R = Ph ( 1 ), CF₃ ( 2 )] were studied experimentally by variable temperature dynamic NMR spectroscopy. Low temperature ¹³C NMR spectra of the two compounds revealed the frozen ring inversion process and approximately equal content of the axial and equatorial conformers. Calculations of the 4‐silathiane derivatives 1 , 2 and the model compound [R = Me ( 3 )] as well as their carbon analogs, the similarly N‐substituted thiane 1‐sulfimides [R = Ph ( 4 ), CF₃ ( 5 ), Me ( 6 )] at the DFT/B3LYP/6–311G(d,p) level in the gas phase and in chloroform solution using the PCM model at the same level of theory showed a strong dependence of the relative stability of the conformer on the solvent. The electronegative trifluoromethyl group increases the relative stability of the axial conformer. Copyright © 2010 John Wiley & Sons, Ltd.