Zhang Wen-tao

Absorption enhancement and sensing properties of Ag diamond nanoantenna arrays

Noble metal nanoantenna could effectively enhance light absorption and increase detection sensitivity. In this paper, we propose a periodic Ag diamond nanoantenna array to increase the absorption of thin-film solar cells and to improve the detection sensitivity via localized surface plasmon resonance. The effect of nanoantenna arrays on the absorption enhancement is theoretically investigated using the finite difference time domain (FDTD) method with manipulating the spectral response by geometrical parameters of nanoantennas. A maximum absorption enhancement factor of 1.51 has been achieved in this study. In addition, the relation between resonant wavelength (intensity reflectivity) and refractive index is discussed in detail. When detecting the environmental index using resonant wavelengths, a maximum detection sensitivity of about 837 nm/RIU (refractive index unit) and a resolution of about 10−3 RIU can be achieved. Moreover, when using the reflectivity, the sensitivity can be as high as 0.93 AU/RIU. Furthermore, we also have theoretically studied the effectiveness of nanoantennas in distinguishing chemical reagents, solution concentrations, and solution allocation ratios by detecting refractive index. From the results presented in this paper, we conclude that this work might be useful for biosensor detection and other types of detections.

Research of optical diffraction properties on surface pit array light-trapping structure

Pit array structure has a good light-trapping characteristic, which can effectively reduce the surface light reflection and prolong the optical path. Therefore in the photo voltaic field, especially in the thin film silicon solar cells field, the pit array structure has good prospects. In this paper, a combining method of theory analysis and experimental verification was used to research the optical diffraction characterizes of the surface pit array light-trapping structure, and the effect of diffraction on the absorption characteristics of silicon thin-film solar cells was discussed. The results show that the greater the aspect ratio of the pit arrays, the better effect of the diffraction, which is more advantageous for uniform scattering of light, and more contribution to the absorption of the incident light and the improvement of the efficiency for the solar cells. Another, the diffraction characteristics of the pit structure are also related to the wavelength of the incident wave. The longer the incident wavelength is, the better the diffraction effect is. This paper research is of important reference value for the design of high-efficiency light-trapping arrays and diffraction grating.

The influence of divergence angle on the deposition of neutral chromium atoms using a laser standing wave

The characteristics of neutral chromium atoms in the standing wave field are discussed. Based on a semi-classical model, the motion equation of neutral atoms in the laser standing wave field is analyzed, and the trajectories of the atoms are obtained by simulations with the different divergence angles of the atomic beam. The simulation results show that the full width at half maximum (FWHM) of the stripe is 2.75 nm and the contrast is 38.5: 1 when the divergence angle equals 0 mrad, the FWHM is 24.1 nm and the contrast is 6.8:1 when the divergence angle equals 0.2 mrad and the FWHMs are 58.6 and 137.8 nm, and the contrasts are 3.3: 1 and 1.6: 1 when the divergence angles equal 0.5 and 1.0 mrad, respectively.

Performance enhancement of poly(N-vinycarbazole) with Covalently Bonded C 60 for photovoltaic application

The performance of a photovoltaic device composed of poly(N-vinylcarbazole) with Covalently Bonded C<inf>60</inf> (PVK- C<inf>60</inf>) exhibits a significant improvement compared with its corresponding simple poly(N-vinylcarbazole) and C<inf>60</inf> blend under the same condition. The open circuit voltage (Voc) is increased from 0.25V for their blend to more than 1V for PVK-C<inf>60</inf> copolymer. In PVK-C<inf>60</inf> copolymer, the carbazole block acts as donor and covalently attached fullerene (C<inf>60</inf>) acts as acceptor. The absorption edge of PVK-C<inf>60</inf> extends through the entire visible spectrum, while their blend has very weak absorption in this range. PL spectrum shows that there is more obvious spectrum quenching for PVK-C<inf>60</inf> copolymer than their blend which implies well-mixed states of donor (carbazole) and acceptor (C<inf>60</inf>) in PVK-C<inf>60</inf> copolymer.

Analysis of Nanometer Structure for Chromium Atoms in Gauss Standing Laser Wave

The equation of motion of two-level chromium atoms in Gauss standing laser wave is discussed and the distribution of chromium atoms is given under different transverse velocity conditions. The results show that the focusing position of atoms will be affected by the transverse velocity of atoms. Based on the four-order Runge-Kutta method, the locus of chromium atoms in Gauss standing laser wave is simulated. The three-dimensional characteristics of nanometer structures are stimulated under perfect and emanative conditions.