High efficiency and stable dye-sensitized solar cells with an organic chromophore featuring a binary pi-conjugated spacer

We employed a binary spacer of orderly conjugated 3,4-ethyldioxythiophene and thienothiophene to construct a wide-spectral response organic chromophore for dye-sensitized solar cells, exhibiting a high power conversion efficiency of 9.8% measured under irradiation of 100 mW cm(-2) air mass 1.5 global (AM1.5G) sunlight and an excellent stability.

Photocurrent response in a double barrier structure with quantum dots-quantum well inserted in central well

We report the photocurrent response in a double barrier structure with quantum dots-quantum well inserted in central well. When this quantum dots-quantum well hybrid heterostructure is biased beyond + 1 or -I V, the photocurrent response manifests itself as a steplike enhancement, increasing linearly with the light intensity. Most probably, at proper bias condition, the pulling down of the X minimum of GaAs at the outgoing interface of the emitter barrier by the photovoltaic effect in GaAs QW will initiate the r,-X-X tunneling at much lower bias as compared with that in the dark. That gives rise to the observed photocurrent response. (c) 2006 Elsevier B.V. All rights reserved.

Peculiar photocurrent response due to Gamma-X coupling in a GaAs/AlAs heterostructure

Peculiar current jumps and hysteresis in current-voltage curves are reported in an illuminated heterostructure consisting basically of a thick AlAs layer and a narrow GaAs quantum well. These novel features come from the photon-assisted transfer of electron-hole pairs and the resultant charge polarization in the structure, mainly caused by the resonant Gamma-X coupling at the heterointerfaces. Using the transfer-matrix method, the simulated current density-voltage curve reproduces the main features of the experimental observations in the case where the influence of resonant Gamma-X coupling at the heterointerfaces is included, further confirming the physical mechanism involved. The structure presented here may be used as a new type of photonic memory cell and also as an optically controlled switch.

Spectral dependence of spin photocurrent and current-induced spin polarization in an InGaAs/InAlAs two-dimensional electron gas

The converse effects of spin photocurrent and current induced spin polarization are experimentally demonstrated in a two-dimensional electron gas system with Rashba spin splitting. Their consistency with the strength of the Rashba coupling as measured for the same system from beating of the Shubnikov-de Haas oscillations reveals a unified picture for the spin photocurrent, current-induced spin-polarization, and spin-orbit coupling. In addition, the observed spectral inversion of the spin photocurrent indicates a system with dominating structure inversion asymmetry.

Constrained high-order statistical blind deconvolution of spectral data

A constrained high-order statistical algorithm is proposed to blindly deconvolute the measured spectral data and estimate the response function of the instruments simultaneously. In this algorithm, no prior-knowledge is necessary except a proper length of the unit-impulse response. This length can be easily set to be the width of the narrowest spectral line by observing the measured data. The feasibility of this method has been demonstrated experimentally by the measured Raman and absorption spectral data.

A new type of photoelectric response in a double barrier structure with a wide quantum well

We have calculated the photoelectric response in a specially designed double barrier structure. It has been verilied that a transfer of the internal photovoltaic effect in the quantum well to the tunnelling transport through above-barrier quasibound states of the emitter barrier may give rise to a remarkable photocurrent.

Finite-difference time-domain analysis of deformed square cavity filters with a traveling-wave-like filtering response by mode coupling

An add-drop filter based on a perfect square resonator can realize a maximum of only 25% power dropping because the confined modes are standing-wave modes. By means of mode coupling between two modes with inverse symmetry properties, a traveling-wave-like filtering response is obtained in a two-dimensional single square cavity filter with cut or circular corners by finite-difference time-domain simulation. The optimized deformation parameters for an add-drop filter can be accurately predicted as the overlapping point of the two coupling modes in an isolated deformed square cavity. More than 80% power dropping can be obtained in a deformed square cavity filter with a side length of 3.01 mu m. The free spectral region is decided by the mode spacing between modes, with the sum of the mode indices differing by 1. (c) 2007 Optical Society of America.

Radiation-use efficiency and the harvest index of winter wheat at different nitrogen levels and their relationships to canopy spectral reflectance

Radiation-use efficiency (RUE, g/MJ) and the harvest index (HI, unitless) are two helpful characteristics in interpreting crop response to environmental and climatic changes. They are also increasingly important for accurate crop yield simulation, but they are affected by various environmental factors. In this study, the RUE and HI of winter wheat and their relationships to canopy spectral reflectance were investigated based on the massive field measurements of five nitrogen (N) treatments. Crop production can be separated into light interception and RUE. The results indicated that during a long period of slow growth from emergence to regreening, the effect of N on crop production mainly showed up in an increased light interception by the canopy. During the period of rapid growth from regreening to maturity, it was present in both light interception and RUE. The temporal variations of RUEAPAR (aboveground biomass produced per unit of photosynthetically active radiation absorbed by the canopy) during the period from regreening to maturity had different patterns corresponding to the N deficiency, N adequacy and N-excess conditions. Moreover, significant relationships were found between the RUEAPAR and the accumulative normalised difference vegetation index (NDVI) in the integrated season (R-2 = 0.68), between the HI and the accumulative NDVI after anthesis (R-2 = 0.89), and between the RUEgrain (ratio of grain yield to the total amount of photosynthetically active radiation absorbed by the canopy) and the accumulative NDVI of the whole season (R-2 = 0.89) and that after anthesis (R-2 = 0.94). It suggested that canopy spectral reflectance has the potential to reveal the spatial information of the RUEAPAR, HI and RUEgrain. It is hoped that this information will be useful in improving the accuracy of crop yield simulation in large areas.

A STUDY OF THE SPECTRUM PROPERTIES AND THE PHOTOVOLTAGE RESPONSE OF NANOCRYSTALLINE ND2O3

The diffuse reflectance spectra of nanocrystalline Nd2O3 were measured in the ultraviolet-visible region, It is found that the part of f-->f transition bands were widened and red-shift occurred. The absorption tail-band in the region from 300 to 550 nm was assigned to the O-2p-->Nd-4f transition. The behavior of light-induced charge transfer and photovoltaic properties of nanocrystalline Nd2O3 were studied by the surface photovoltage spectroscopy (SPS) and electric field modulating SPS techniques. The SPS response shows two peaks at 330 nm(P-1) and 380 nm(P-2) in the UV-Vis range, The spectral features observed can be explained in terms of charge transfer and interband transition.