Herein, simple and scalable approach to enhance the out‐coupling efficiency in organic light‐emitting diodes (OLEDs) is presented. By exposing the 4,4′‐bis[ N ‐(1‐naphthyl‐1‐)‐ N ‐phenylamino]‐biphenyl (NPB) hole transport layer to hydrofluoroether (HFE) solvent for several minutes, a controllable microroughening of the film is achieved, which results in the formation of random scattering centers in the OLED structure. Optimized NPB microroughening for phosphorescent OLED with Ir(ppy)3 emitter leads to luminous efficacy improvement of 23% (from 64 to 79 lm W −1 at 1000 cd m −2 ) without additional external out‐coupling. Angular resolved spectroscopy of the OLED with an internal scattering layer reveals constant color almost independent of the viewing angle and Lambertian intensity distribution.

The second-harmonic generation in CH3NH3PbI3 (MAPI) perovskite multidomain thin films is experimentally studied. The MAPI nonlinear second-order susceptibility is estimated. Polarization of MAPI SHG signal is experimentally observed and hyper-Rayleigh scattering angle value is estimated.

Methylammonium lead iodide is a benchmark hybrid organic perovskite material used for low-cost printed solar cells with a power conversion efficiency of over 20%. Nevertheless, the nature of light–matter interaction in hybrid perovskites and the exact physical mechanism underlying device operation are currently debated. Here, we report room temperature, ultrafast photocurrent generation, and free-space terahertz emission from unbiased hybrid perovskites induced by femtosecond light pulses. The polarization dependence of the observed photoresponse is consistent with the bulk photovoltaic effect caused by a combination of injection and shift currents. Observation of this type of photocurrents sheds light on the low recombination and long carrier diffusion lengths arising from the indirect bandgap in CH 3 NH 3 PbI 3 . Naturally ballistic shift and injection photocurrents may enable third-generation perovskite solar cells with efficiency exceeding the Shockley–Queisser limit. The demonstrated control over photocurrents with light polarization also opens new venues toward perovskite spintronics and tunable THz devices.

We report on a saturable absorption in aqueous dispersions of nanodiamonds with femtosecond laser pulse excitation at a wavelength of 795 nm. The open aperture Z-scan experiments reveal that in a wide range of nanodiamond particle sizes and concentrations, a light-induced increase of transmittance occurs. The transmittance increase originates from the saturation of light absorption and is associated with a light absorption at 1.5 eV by graphite and dimer chains (Pandey dimer chains). The obtained key nonlinear parameters of nanodiamond dispersions are compared with those of graphene and carbon nanotubes, which are widely used for the mode-locking. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).

Organohalide lead (hybrid) perovskites have emerged as competitive semiconducting materials for photovoltaic devices due to their high performance and low cost. To further the understanding and optimization of these materials, solution-based methods for interrogating and modifying perovskite thin films are needed. In this work, we report a hydrofluoroether (HFE) solvent-based electrolyte for electrochemical processing and characterization of organic-inorganic trihalide lead perovskite thin films. Organic perovskite films are soluble in most of the polar organic solvents, and thus until now, they were not considered suitable for electrochemical processing. We have enabled electrochemical characterization and demonstrated a processing toolset for these materials utilizing highly fluorinated electrolytes based on a HFE solvent. Our results show that chemically orthogonal electrolytes based on HFE solvents do not dissolve organic perovskite films and thus allow electrochemical characterization of the electronic structure, investigation of charge transport properties, and potential electrochemical doping of the films with in situ diagnostic capabilities.

We present experimental and theoretical study of the femtosecond light-assisted field electron emission from nanocarbon films. We demonstrate that irradiation with intense femtosecond laser pulse allows one to achieve electron emission density of up to 13 nC/cm2 at a moderate applied static electric filed. The developed model well describes obtained experimental results and allows us to visualize physical mechanisms including heating of electron gas, multiphoton photoionization, and the space charge formation, which are responsible for the observed phenomena.

Organohalide lead perovskite (CH3NH3PbI3) is a novel material with promising applicability for visible light photo‐detectors. The ability to develop perovskite photo‐detector devices using a low temperature solution based process allows straightforward combinations with other materials, including traditional crystalline semiconductors, with minimal contributions to cost and process complexity. There is, however, a need for high‐resolution structuring of the perovskite film to minimize cross‐talk between neighboring detectors (pixels) for imaging purposes. This work presents a method to develop Ch3NH3PbI3 thin films possessing high‐resolution patterning, using lithography processing with hydrofluoroether solvents. The results presented herein confirm that, unlike the majority of traditional solvents utilized in conventional photolithography, hydrofluoroethers do not adversely affect CH3NH3PbI3 films, enabling photolithographic processing. Transfer of the resist pattern is achieved using a SF6 plasma functionalization process which extracts iodine and organic components from the film, converting the perovskite into PbF2. This work also demonstrates that isolation of perovskite photodetecting pixels with a 20 μm‐wide stripe of PbF2 leads to a 4.5‐fold reduction in the cross‐talk between neighboring pixels. It is believed that our method will facilitate simple monolithic integration of perovskite photodiodes to the silicon backplane chip utilized in active‐pixel sensor and charge‐coupled device applications.

No abstract is available for this article.

CH3NH3PbI3 deposited on a ZnO electron transport layer is chemically unstable and decomposes at >80 degrees C, leaving PbI2 on the substrate along with traces of iodine. We found that this decomposition was reversible and could be prevented if a restricted volume solvent annealing procedure was applied. We also found that decomposition requires the presence of a certain amount of the processing solvent within the film. Finally, we developed a reliable annealing protocol for depositing perovskite film on ZnO, which resulted in the generation of repeatable solar cell devices.

We have developed capacitively-transduced nanomechanical resonators using sp(2)-rich diamond-like carbon (DLC) thin films as conducting membranes. The electrically conducting DLC films were grown by physical vapor deposition at a temperature of 500 °C. Characterizing the resonant response, we find a larger than expected frequency tuning that we attribute to the membrane being buckled upwards, away from the bottom electrode. The possibility of using buckled resonators to increase frequency tuning can be of advantage in rf applications such as tunable GHz filters and voltage-controlled oscillators.

We report on the fabrication of high-mobility organic thin-film transistors (OTFTs) made and tested under ambient conditions. A bottom gate, bottom contact architecture was used with a layer of poly(3-hexylthiophene) deposited on a 50 nm thick Al2O3 dielectric with pre-patterned Au source and drain electrodes. Fluoroalkyl trichlorosilane treatment of the Al2O3 dielectric was found to significantly improve device performance. The field-effect hole mobility reproducibly reached 0.2 cm2 V−1 s−1 (best device 0.29 cm2 V−1 s−1) with an on/off ratio of 104. Electrical and synchrotron X-ray scattering characterization shows that an interaction at the FOTS/P3HT interface is responsible for the high performance of these devices. The fabrication method described here is carried out under ambient conditions and does not require any post-deposition annealing or vacuum drying steps for the organic film; therefore it can simplify the manufacturing of OTFTs.

A diode pumped passively mode-locked YAG:Nd laser operated at wavelength 1.32 μm has been developed using a novel saturable absorber based on single-wall carbon nanotubes incorporated in a polymer matrix. Laser pulses with the output energy up to 70 μJ and the duration of 50 ps have been generated. A stable mode-locking regime has been obtained with the pump frequency up to 1 kHz. The femtosecond time-resolved measurements of the nonlinear absorption coefficient of the nanotube-based saturable absorber have been performed. In the spectral range of 1.2-1.45 μm, the third-order optical susceptibility of the carboxymetylcellulose film with incorporated single-wall HiPCO carbon nanotubes has been found to be as high as 10 -12 esu. The characteristic time of the fast component of the electronic relaxation was estimated as 200 fs.

We demonstrate that in graphitic nanocarbon materials, combination of ballistic conductivity and strong electron photon coupling opens a unique opportunity to observe transfer of momentum of the electromagnetic radiation to free carriers. The resulting drag of quasiballistically propagating electrons can be employed, in particular, to visualize the temporal profile, polarization, and propagation direction of the laser pulse. In this letter, we report the giant photon drag effect in yarns made of multiwall carbon nanotubes.

By tuning wavelengths of the femtosecond pump and probe pulses we mapped the nonlinear absorption of copper-glass nanocomposites within 520-620 nm range. At the pump intensity of 3 GW/cm(2), the induced transmission rise was as high as 20%. The imaginary part of the third-order optical susceptibility of the nanocomposites as a function of the probe wavelength reproduced well the spectral profile of the surface plasmon resonance in copper. In contrast, the imaginary part of the third-order optical susceptibility as a function of the pump wavelength did not reproduce the plasmon profile being wider than the latter.

We demonstrate that a strong light-induced electric signal generated in nanographite reproduces shape of nanosecond light pulses in the interval 260-5000 nm. This indicates that nanographite can be employed in ultrafast light detectors.

We demonstrate that irradiation with nano-second light pulses results in significant enhancement of the electron emission from nano-graphite films. The observed emission current density is as high as 10 A/cm(2) at applied field of 2 V/mu m. The duration of the emission pulse depends on the applied DC voltage and laser intensity. However, in our experimental conditions, the temporal profile of the electron pulse nearly reproduces that of the incident laser pulse. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In this work field electron emission was studied for a variety of single-wall carbon nanotube-based nanostructures (arc and HipCO nanotubes, C-60-and C-70-based carbon peapods, double-wall nanotubes) in the same conditions. A comparable surface roughness for all samples was confirmed by a scanning electronic microscopy, while distribution of emission centers was visualized with a phosphorescent anode screen. We developed an original approach that improves a reliability of the field emission threshold measurements. All materials showed the emission threshold values ranging from 0.5 to 2.5 V/mu m. The lowest threshold was observed for HipCO and double-wall materials that contain thinner nanotubes than other studied materials.