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The high photoluminescence efficiency, high color purity, and easy tunable bandgap make inorganic perovskite nanocrystals very attractive in luminescent display applications. Here, we report a color-saturated, red light-emitting diode (LED) using an inverted organic/inorganic hybrid structure and perovskite nanocrystals. We demonstrated that through a simple post treatment to the perovskite nanocrystals with polyethylenimine, the surface defects of the perovskite nanocrystals could be well passivated, leading to great enhancements on their absolute photoluminescence quantum yield and photoluminescence lifetime. Through using a well-passivated perovskite nanocrystal film and optimizing the charge balance, we achieved an electroluminescence LED with a current efficiency of 3.4 cd A–1, corresponding to an external quantum efficiency (EQE) of 6.3%, which is the highest value reported among perovskite NC LEDs so far.

We fabricated a series of infrared (IR)-transparent and conductive Sn-doped CuScO2 thin films using a polymer-assisted deposition (PAD) method. Highly c-axis oriented films were grown on a-plane sapphire substrates, and the orientation relationship with respect to the substrates was confirmed to be CuScO2:Sn[3R](0001)//a-Al2O3(110). The films exhibited good p-type conductive characteristics, and a high conductivity of 17.86 S cm−1 was achieved for CuSc0.94Sn0.06O2 at room temperature, which is 19 times larger than the un-doped film at room temperature. The prepared films retain a transparency of >70% in the near-IR region and >90% in the mid-IR region, which are the best performing p-type IR transparent conductive thin films grown by chemical solution methods to date. As x changes from 0 to 0.06, the hopping activation energy varies within the range of 129–98 meV. As an application of such films, p-CuScO2:Sn/n-ZnO heterojunction diodes were fabricated using the PAD technique. The measured ∼2 V threshold voltage of the p-CuSc0.94Sn0.06O2/n-ZnO diode is in reasonable agreement with the bandgap energy of CuSc0.94Sn0.06O2. The resulting films can be used in optoelectronic devices over a wide wavelength range from the visible to IR band, due to their high electrical conductivity and optical transparency.

A p-type organic thin film transistor (OTFT) was fabricated based on an axially-substituted phthalocyanine (titanium phthalocyanine dichloride: TiCl2Pc). Molecular energies and atomic charge distributions of a series of axially-substituted metal phthalocyanines were studied using measurements of their electrochemical properties and X-ray photoemission spectroscopy, respectively. Based on these measurements, the relationship between the charge carrier transport types of the phthalocyanines in OTFTs and their substituted groups (metal and axial ligands) are discussed. The axially-substituted electron-withdrawing groups can effectively lower the LUMO energy and increase the charge separation, contributing to the realization of n-type behavior, e.g. in SnCl2Pc. The electronegativity of the metal also affects the LUMO energies and charge distributions, such that TiCl2Pc is a p-type semiconductor.

A broadband-absorption enhancement in two kinds of polymer-based organic solar cells (OSCs) is demonstrated in this work by employing micro-nano composite gratings (MNCGs). The structure of MNCGs is nano-grating covering on the surface of micro-grating. By embedding the MNCGs at the interface of the active layer/Ag cathode, the multi-absorption-enhancement mechanisms, such as dual-microcavity resonance, plasmon-cavity polaritons and light-scattering effects, are excited and result in a broadband-absorption enhancement. The light absorption of active layer in the MNCG-based OSC is numerically calculated. As a result, comparing to the planar OSCs, the absorption intensity is increased by 50.41% and 20.43% in these two kinds of polymer-based OSCs, respectively. Meanwhile, the MNCGs can also be universally used in all kinds of polymer-based OSCs to increase the light absorption of the active layer.

Delafossite-type CuCr1−x Zn x O2 (x = 0, 0.03, 0.05, 0.07, 0.1) conductive oxides were synthesized by sol–gel method, and the effects of Zn-doping on morphology, structure, and electrical properties of the CuCr1−x Zn x O2 oxides were investigated. Based on X-ray diffraction (XRD) and Raman spectrum, the crystalline quality of the oxides is improved by the suitable substitution of Cr by Zn. The X-ray photoelectron spectroscopy (XPS) spectra reveal the chemical state of Zn is +2. The Hall and Seebeck coefficients of the pellet samples display a positive sign, indicating p-type conductive characteristics of the obtained oxides. The temperature-dependent resistivity of the oxides is proven to be consistent with small polaron hopping. For the three oxide samples with x = 0, 0.05, and 0.1, the activation energies for the polaron hopping between Zn2+ and Cr3+ sites are 54, 41.5, 32 meV, respectively, which is found to decrease with the increase of Zn content. The electrical conductivity can be remarkably improved by Zn-doping due to the small polaron hopping activation energy. These properties render this material promising as transparent electrode in optoelectronic industry.

Epitaxial thin films of CuFe 1 − x Sn x O 2 ( x = 0.00, 0.01, 0.03, 0.05, 0.07), a transparent oxide semiconductor with delafossite structure, were grow on Al 2 O 3 (0 0 0 1) substrate by sol–gel method, The X-ray diffraction patterns revealed that the CuFeO 2 film annealed at 500 °C in air was mainly composed of amorphous phase, and after post-annealed at 900 °C in N 2 , single phase CuFe 1 − x Sn x O 2 films with high c -axis oriented were obtained. The Raman spectrum confirmed the delafossite structure of the films. The binding energy of Cu-2p 3/2 , Fe-2p 3/2 and Sn-3d 5/2 were 932 eV, 711.3 eV and 486.2 eV in CuFe 1 − x Sn x O 2 films. The chemical composition of the films was close to its stoichiometry, which was determined by X-ray photoelectron spectroscopy. The films show high transmittance around 45–78% in the visible band and 78–95% in the near infrared spectral region, while the energy gaps for direct allowed transition were estimated as 3.5 ± 0.02 eV. The p-type characteristics of CuFe 1 − x Sn x O 2 thin films were determined by positive Hall coefficients. The resistivity of the film was 36.83 Ω cm for CuFeO 2 film at room temperature, significantly decreased to 1.043 Ω cm after substituting Sn 2+ for Fe 3+ . The resistivity showed a decrease at the beginning and increased with the growing of Sn ion doping ratio. These results demonstrate that the high c -axis oriented CuFe 1 − x Sn x O 2 films can be the very promising p-type transparent conductive thin films.

One-dimensional, diluted magnetic semiconductor nanofibers have attracted increasing attention for their unique magnetic properties, large specific surface area, and high porosity. These qualities lead to excellent performance in magneto-optical devices, magnetic resonance imaging, ferrofluids and magnetic separation. The purpose of this study is to fabricate P-type one dimensional CuAlO2-based diluted magnetic semiconductor nanofibers. First, we fabricated CuAl0.95Co0.05O2 nanofibers with an average diameter of 1 μm with the electrospinning method. The annealed nanofibers were thermally treated at a temperature of 1 100 °C and then shrunk to a diameter of about 650 nm. We used X-ray diffraction measurements and Raman spectra to confirm that the CuAl0.95Co0.05O2 nanofibers had a single impurity free delafossite phase. The X-ray photoelectron spectroscopy analysis indicates that Co was present in the +2 oxidation state, resulting in an room temperature ferromagnetism in the CuAl0.95Co0.05O2 fiber. This contrasts with nonmagnetism in pristine CuAlO2 fiber. The coercivity (H c) value of 65.26 Oe and approximate saturation magnetization (M s) of 0.012 emu/g demonstrate good evidence of ferromagnetism at room temperature for CuAl0.95Co0.05O2 nanofibers.

As an important wide bandgap p-type conductive delafossite material, CuScO2 (CSO) has been intensively investigated for its wide applications in multi-functional optoelectronic devices. In order to obtain both high infrared (IR) transparency and low resistivity, we report on, for the first time, the experimental preparation of single phase epitaxial CSO thin film by using polymer-assisted-deposition (PAD) method. As a key point in the PAD process, the used polymer materials (PEI and EDTA) not only control the desired viscosity for the process, but also bind the metal ions to prevent premature precipitation and formation of metal oxide oligomers. The technique results in a homogeneous distribution of the metal precursors in the solution as well as the formation of uniform metal organic film. Due to the uniaxial locked epitaxy mechanism, the epitaxial growth of CSO (0001) thin film on a-plane sapphire is achieved, and the orientation relationship of the film with respect to the substrate are confirmed to be CSO[3R](0001)//a-Al2O3(110). The obtained CSO thin film from the PAD technique exhibits a low electrical resistivity of 1.047 Ω cm at room temperature, and a high transmittance of 65–85% in the near-IR range and more than 85% in the mid-IR range. The presented technique does provide the possibility of preparing high-crystallinity oxide films which can be applicable over a wide wavelength range from visible band to infrared band.

We synthesized CuAl 1− x Co x O 2 ( x = 0.00–0.07) thin films by solid-state reaction from Cu 2 O and Al 2 O 3 on a sapphire (0 0 1) substrate by a simple and cost-effective spin-on technique. X-ray diffraction and Raman spectroscopy confirm the formation of single impurity-free delafossite CuAlO 2 structure for all the compositions. We observed diamagnetism for pristine CuAlO 2 and ferromagnetism for Co-doped CuAlO 2 at room temperature. Specially, the coercivity ( H c ) and saturation magnetization ( M s ) are significantly enhanced with Co composition from 1 at.% to 5 at.% but show the reverse tendency with higher Co content.