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Side-chain engineering plays a significant role in the design of conjugated materials. In this work, a series of conjugated polymers PBDB-T-R with functionalized groups at the end of side units were developed as electron donor for organic solar cells (OSCs). The donor polymers PBDB-T-I and PBDB-T-OAc with iodine and acetate end groups exhibited similar absorption and energy levels, but showed much improved PCEs in OSCs compared to the polymer PBDB-T-H without substitutions at the end groups. Additionally, we found that PBDB-T-I and PBDB-T-OAc based cells exhibited optimized performance when using chloroform as solution-processed solvent without any additives. These results indicate that these conjugated polymers can act as self-additive to fabricate photoactive layers via solution process in OSCs.

A gate electrode is usually used to controllably tune the carrier concentrations, further modulating the electrical conductivity and the Seebeck coefficient to obtain the optimum thermoelectric figure of merit (ZT) in two-dimensional materials. On the other hand, it is necessary to investigate how an electric field induced by a gate voltage affects the electronic structures, further determining the thermoelectric properties. Therefore, by using density functional calculations in combination with Boltzmann theory, the thermoelectric properties of bilayer MX

The J-V curve measurment and AFM technology were applied to study the relationship between P3HT:PCBM heterojunction film solar cell devices photovoltics parameter and blend solution concentration and annealed time of this device. The Voc, Jsc, FF and PCE of device were obtained from the device prepared by three blend solution concentration respectively. Data show that with increasing solution concentration PCE of solar cell device do not always improve and it achieves maximum when concentration is 20 mg/mL. Result indicates that only when solar cell device has active layer with proper thickness its performance will achieve the best effect. Additionally, photovoltaic parameters from four sample prepared by different annealed time were obtained also. Results indicate that the device with proper annealed time of 20 min at 130°C can achieve the best effect.

The response mechanism of a vertical alignment mode, driven by a fringe field, is investigated in detail using small-angle approximation. The flow effects can be ignored when using theoretical analysis. The period of the liquid crystal (LC) deformation in the transversal direction, instead of the lognitudinal direction, shows the cell gap effect on the response time in the LC layer's thickness. The authors' analytical results indicate that a liquid crystal display (LCD) mode with a small transversal period could provide a new method that gives a fast response.

The response times of Pi‐cell liquid crystal displays with an arbitrary pretilt angle were calculated under different drive methods. Using the normal drive method, the results show that the rise and off times of the cell driven by high voltage are faster than those driven by low voltage. However, the off time is very fast for the cell with non‐zero critical voltage driven by low voltage when we use the under‐shoot method.

The nano-Ag films were prepared by RF magnetron sputtering technique, and all of them were treated by rapid thermal annealing at different temperatures. The structure, the morphology and the optical properties of the annealed nano-Ag films were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis-NIR spectroscopy. The experimental results show that the open area fraction of the film and spacing between islands or nanoparticles increase with the increase of the annealing temperature, while the aspect ratio decreases. The anisotropic worm-like island films have been reshaped into isotropic nanospheres. The surface plasmon (SP) resonance band blue shifts and narrows continuously with increasing heating temperature. Analyses show that the SP resonance of the nano-Ag films can be modulated by morphology evolution induced by rapid thermal annealing.

A bluish green Ca7 (SiO4)2Cl6 : Eu2+ phosphor used for UV excited white LED was synthesized by high temperature solid state method. The XRD patterns and luminescence properties were investigated. The results indicated that the sample was single Ca7 (SiO4)2Cl6 phase; the emission spectrum included two emission peaks located at 418 and 502 nm, respectively. Monitoring for the two emission peaks, the excitation spectra were two broad band peaks centered at 290 and 360 nm respectively, which illustrated that Eu2+ ions located at two different crystal lattice sites. The influence of Eu2+ ions concentration on the luminescence intensity was studied and the optimal doping concentration was 0.75 mol%. The results showed that this phosphor was a better candidate bluish phosphor for UV based white LED.

The LiSrBO3:Dy3+ phosphor was synthesized by solid-state method. SrCO2 (99.9%), Li2CO3 (99.9%), H3BO3 (99.9%) and Dy2O3 (99.9%) were used as starting materials. After these individual materials were blended and grounded thoroughly in an agate mortar, the homogeneous mixture was heated at 700 degrees C for 2 h in air, and LiSrBO3:Dy3+ phosphors were obtained. The phase present of the samples was characterized by powder X-ray diffraction (XRD) (D/max-rA, Cu Kalpha, 40 kV, 40 mA, lamda = 0.15406 nm). The excitation and emission spectra of these phosphors were measured by a RF-540 photoluminescence spectrophotometer. The emission spectrum of LiSrBO3:Dy3+ phosphor shows several bands at 486, 578 and 668 nm, respectively. The excitation spectrum for 578 nm emission has several excitation bands at 331, 368, 397, 433, 462 and 478 nm, respectively. The effect of Dy3+ concentration on the emission intensity of LiSrBO3:Dy3+ was investigated, and the result shows that the emission intensity of LiSrBO3:Dy3+ phosphor firstly increases with increasing Dy2+ concentration, then decreases, viz. the concentration quenching exists. And the Dy3+ concentration corresponding to the maximal emission intensity is 3 mol%, and the concentration quenching mechanisms are the d-d interaction by Dexter theory.

Nanocrystalline silicon carbide (nc-SiC) thin films were deposited by helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) technique at different hydrogen dilution ratio (RH). The PL peak energy and intensity were systemically analyzed using photoluminescent (PL) and photoluminescent excitation (PLE) methods. As a whole, the PL intensity shows an increasing trend and the PL peak energy presents continuous blue shifts with increasing hydrogen dilution ratio. In addition, it is found that the spectra band of samples deposited at low RH are composed of two components, the high energy band comes from quantum confinement effect and the low energy band is related to radiation of surface defect. The low energy band has a decreasing trend with increasing hydrogen dilution ratio and even disappears finally at high RH. We explain dependence of PL properties in terms of the variation of film microstructure induced by hydrogen dilution during film deposition. The increasing of PL intensity and the decreasing of the low energy band can both be accounted by the microstructure improvement. The decrease of PL peak energy is related to the size decrease of SiC nanocrystals.

Non-stoichiometric hydrogenated amorphous silicon nitride (a-SiNx : H) film was deposited by helico-wave plasma-enhanced chemical vapour deposition (HWP-CVD) technique. The microstructure and bonding characteristics of both as-deposited and annealed thin films were studied. Raman scattering measurement shows that excess silicon exists in the form of amorphous silicon particles in the as-deposited sample. The microstructure of crystalline nano-particles silicon embedded in silicon nitride matrix in the post-annealed sample was formed. Comparing the results of both the Fourier transform infrared spectra and the optical absorption spectra of the samples deposited under different conditions, it is shown that the microstructure of the thin film depended on the gas flow ratio and annealing process. The sample with lower excess silicon shows a lower density of defect state at the silicon nanocrystal/SiNx interface due to a higher binding hydrogen content. The annealing process induces the decrease in Si-H and N--H binding densities. Because of the formation of silicon nanocrystals, the annealed samples exhibit a higher structure disorder degree.

The time-resolved spectra of free photoelectrons and shallow-trapped electrons in the T-grains AgBrI emulsion were simultaneously detected with microwave absorption and dielectric spectrum detection technique. The results indicate that the electron trap effects of sulfur sensitization centers and sulfur-plus-gold sensitization centers are different with equal quantities of Na2S2O3 added. The sulfur sensitization centers acted as a deep electron trap to pick up the electronic decay because of increasing the number of deep trapped electrons, while the sulfur-plus-gold sensitization centers as a shallow electron trap decrease the electronic decay through effectively controlling the recombination between the electrons and the holes. The depth of sulfur-plus-gold sensitization center is shallower than that of sulfur sensitization center after the KAuCl4 is added. The effects of sulfur sensitization center and sulfur-plus-gold sensitization center on the photoelectron decay are different in different sections of decay curves through the change in electron time-resolved spectra.

Nanocrystalline silicon carbon (nc-SiC) from amorphous silicon carbon films was obtained through XeCl excimer laser annealing. The photoluminescence (PL) of the nc-SiC was analyzed at different annealing laser energy density. It was observed that PL presented a wide luminescence band from 300-600 nm in the nc-SiC films. The two main luminescence bands, situated at 398 and 470 nm respectively, are attributed to band to band and defect recombination in the 6H-SiC based on the structure changes of the nc-SiC films. The relative PL intensity of these two bands was determined by the surface state density in the nc-SiC films and their irradiative life

Microwave absorption and film dielectric spectrum detection technology was used to study the influence of complex K4Ru (CN)6 on the photoelectron decay time-resolved spectrum of cubic AgCl crystals illuminated in this paper. The results indicate that the influence of the doping content and doping position of the complex K4Ru(CN)6 on the photoelectron decay time-resolved spectrum is evident. The photoelectron decay process of this emulsion is slowest, and the photoelectron lifetime is longest when doped with K4Ru (CN)6 of 2.45 x 10(-5) mol x (mol Ag)(-1) at doping positions of 75% Ag.

Photoelectrons plays an important role in the latent image formation process of silver halide materials, and the decay characteristic of photoelectrons are dependent on the structure of silver halide microcrystals to a great extent. In this paper, the decay spectra of free photoelectrons and shallow-trapped electrons were obtained by optics and microwave double resonance technology. The depth and density of electron traps in silver halide microcrystals were discussed. Moreover, using the lifetime of free photoelectrons, the optimal doping amount of shallow electron trap dopants was found by analyzing the distribution condition of electron traps in silver halide.

Plasma diagnostics is performed during dc. glow discharge plasma-enhanced chemical vapor deposition (PECVD) on nitride thin films using optical emission spectra. Several molecular bands such as the second positive series of N2 transitions, the first negative series of N2+ and the CN, NH violet bands are identified. Variations of the emission intensities of N2(337.1 nm), N2+(391.4 nm) and CN(388.3 nm) are investigated as the function of the percentage of H2, discharge current and deposition pressure. The related excitation mechanism of the species emission is discussed. Experimental results show that adding a small amount of H2(about 5%) into the gas source will be beneficial to produce all the active species. Higher discharge current will result in an increase of the active species concentration while there is maximum emission intensity at medium gas pressure at about 4 kPa. The collisions between the species, including metastable nitrogen and hydrogen are related with the concentration variations of the measured species. All the results and discussion provide reference data for optimizing the deposition parameters and controlling the deposition process in the synthesis of carbon nitride thin films.