Mesh size control in forming an Ag/AgO nano-network structure for transparent conducting application

The variation behaviors of the morphology, transmission, and sheet resistance of the surface Ag/AgO nano-network (NNW) structures fabricated under different illumination conditions and with different Ag deposition thicknesses and thermal annealing temperatures in forming initial Ag nanoparticles (NPs) are studied. Generally, an NNW structure with a smaller mesh size or a denser branch distribution has a lower transmission and a lower sheet resistance level. Under the fabrication condition of a broader illumination spectrum, a lower thermal annealing temperature, or a thicker Ag deposition, we can obtain an NNW structure of a smaller mesh size. The mesh size of an NNW structure is basically controlled by the seed density of Brownian tree (BT) at the beginning of light illumination. A BT-seed can be formed through a stronger local localized surface plasmon resonance for accelerating Ag oxidation in a certain region. Once an Ag/AgO BT-seed is formed, the surrounding Ag NPs are reorganized to form the branches of a BT. Multiple BTs are connected to form a large-area NNW structure, which can serve as a transparent conductor. Under the fabrication conditions of a broader illumination spectrum, 3-nm Ag deposition, and 100-degree-C thermal annealing, we can implement an NNW structure to achieve ~1.15 micron in mesh size, ~90 Ohm/sq in sheet resistance, and 93-77 % in transmittance within the wavelength range between 370 and 700 nm.

A Printable and Conductive Yield-Stress Fluid as an Ultrastretchable Transparent Conductor

In contrast to ionically conductive liquids and gels, a new type of yield-stress fluid featuring reversible transitions between solid and liquid states is introduced in this study as a printable, ultrastretchable, and transparent conductor. The fluid is formulated by dispersing silica nanoparticles into the concentrated aqueous electrolyte. The as-printed features show solid-state appearances to allow facile encapsulation with elastomers. The transition into liquid-like behavior upon tensile deformations is the enabler for ultrahigh stretchability up to the fracture strain of the elastomer. Successful integrations of yield-stress fluid electrodes in highly stretchable strain sensors and light-emitting devices illustrate the practical suitability. The yield-stress fluid represents an attractive building block for stretchable electronic devices and systems in terms of giant deformability, high ionic conductivity, excellent optical transmittance, and compatibility with various elastomers.

Arylenevinylene Oligomer-Based Heterostructures on Flexible AZO Electrodes

We investigated the optical and electrical properties of flexible single and bi-layer organic heterostructures prepared by vacuum evaporation with a p-type layer of arylenevinylene oligomers, based on carbazole, 3,3′ bis(N hexylcarbazole)vinylbenzene = L13, or triphenylamine, 1,4 bis [4 (N,N’ diphenylamino)phenylvinyl] benzene = L78, and an n-type layer of 5,10,15,20-tetra(4-pyrydil)21H,23H-porphyne = TPyP. Transparent conductor films of Al-doped ZnO (AZO) with high transparency, >90% for wavelengths >400 nm, and low resistivity, between 6.9 × 10−4 Ωcm and 23 × 10−4 Ωcm, were deposited by pulsed laser deposition on flexible substrates of polyethylene terephthalate (PET). The properties of the heterostructures based on oligomers and zinc phthalocyanine (ZnPc) were compared, emphasizing the effect of the surface morphology. The measurements revealed a good absorption in the visible range of the PET/AZO/arylenevinylene oligomer/TPyP heterostructures and a typical injection contact behavior with linear (ZnPc, L78) or non-linear (L13) J-V characteristics in the dark, at voltages <0.4 V. The heterostructure PET/AZO/L78/TPyP/Al showed a current density of ~1 mA/cm2 at a voltage of 0.3 V. The correlation between the roughness exponent, evaluated from the height-height correlation function, grain shape, and electrical behavior was analyzed. Consequently, the oligomer based on triphenylamine could be a promising replacement of donor ZnPc in flexible electronic applications.

Doping Limitation Due to Self-compensation by Native Defects in In-doped Rocksalt CdxZn1-xO

CdO-ZnO alloys (CdxZn1-xO) exhibit a transformation from the wurtzite (WZ) to the rocksalt (RS) phase at a CdO composition of ~70% with a drastic change in the band gap and electrical properties. RS-CdxZn1-xO alloys (x>0.7) are particularly interesting for transparent conductor applications due to their wide band gap and high electron mobility. In this work, we synthesized RS-CdxZn1-xO alloys doped with different concentrations of In dopants and evaluated their electrical and optical properties. Experimental results are analyzed in terms of the amphoteric native defect model and compared directly to defect formation energies obtained by hybrid density functional theory (DFT) calculations. A saturation in electron concentration of ~7x1020cm-3 accompanied by a rapid drop in electron mobility is observed for the RS-CdxZn1-xO films with 0.7≤x<1 when the In dopant concentration [In] is larger than 3%. Hybrid DFT calculations confirm that the formation energy of metal vacancy acceptor defects is significantly lower in RS-CdxZn1-xO than in CdO, and hence limits the free carrier concentration. Mobility calculations reveal that due to the strong compensation by native defects, RS-CdxZn1-xO alloys exhibit a compensation ratio of >0.7 for films with x<0.8. As a consequence of the compensation by native defects, in heavily doped RS-CdxZn1-xO carrier-induced band filling effect is limited. Furthermore, the much lower mobility of the RS-CdxZn1-xO alloys also results in a higher resistivity and reduced transmittance in the near infra-red region (λ>1100 nm), making the material not suitable as transparent conductors for full spectrum photovoltaics.

Computational synthesis of substrates by crystal cleavage

The discovery of substrate materials has been dominated by trial and error, opening the opportunity for a systematic search. We generate bonding networks for materials from the Materials Project and systematically break up to three bonds in the networks for three-dimensional crystals. Successful cleavage reduces the bonding network to two periodic dimensions. We identify 4693 symmetrically unique cleavage surfaces across 2133 bulk crystals, 4626 of which have a maximum Miller index of one. We characterize the likelihood of cleavage by creating monolayers of these surfaces and calculating their thermodynamic stability using density functional theory to discover 3991 potential substrates. Following, we identify distinct trends in the work of cleavage and relate them to bonding in the three-dimensional precursor. We illustrate the potential impact of the substrate database by identifying several improved epitaxial substrates for the transparent conductor BaSnO3. The open-source databases of predicted and commercial substrates are available at MaterialsWeb.org.

A New Strategy for Fabricating Low Haze p-Type Cui Film

As an intrinsic p-type transparent conductor with a wide band gap of 3.1 eV, γ-CuI full of potential has gradually attracted the attention of researchers. However, γ-CuI films deposited by various techniques generally present high haze with a frosted-glass-like appearance, significantly hampering the device’s performance. Herein, a new strategy is proposed, where truly p-type CuI thin films with low haze were successfully synthesized at room temperature. The specular transmittance of CuI film above 85% in the visible region (400-800 nm) can be achieved. The haze of the as-prepared γ-CuI films can be as low as 0.7%. Meanwhile, the as-prepared CuI film possesses a FOM as high as 230 MΩ -1 . This ideal stable p-type optoelectronic performance was a significant achievement among various typical p-type transparent conductive films.