Effects of the vertically switching electric field on the photoelectric properties of polymer-stabilized blue-phase liquid crystal cells using the director model.

This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue-phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays that can be applied to adopting better strategies for developing next-generation LCD devices.

Effects of cell gap on the optoelectronic properties of pure blue-phase liquid crystal devices: estimating the Kerr constant.

In this study, the Kerr constant of pure blue-phase liquid crystal (BPLC) without polymer doping at room temperature and the optoelectronic properties dependent on the cell thickness are explored. The relation between the phase and the voltage in oblique incident light was measured via a reasonable vertical electric field for different thicknesses of BPLC cells. It was found that the Kerr constant formula can be amended with the functions related to the cell gap. This study demonstrates a method to estimate the Kerr constant, especially for cells within a small electrical field, which will benefit optoelectronic applications.

Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting.

Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current-voltage (I-V) characteristics as an indicator to qualify the I-V sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications.

A bifunctional copolymer additive to utilize photoenergy transfer and to improve hole mobility for organic ternary bulk-heterojunction solar cell.

To realize the high efficiency organic photovoltaics (OPVs), two critical requirements have to be fulfilled: (1) increasing the photon energy absorption range of the active layer, and (2) improving charge separation and transport in the active layer. This study reports the utilization of THC8, a novel fluorescence-based polymer containing propeller-shaped di-triarylamine and fluorene moieties in the active layer consisting of poly-3-hexylthiophene and [6,6]-phenyl-C61-butyric acid methyl ester to form a ternary bulk heterojunction. The results showed that the high absorbance and strong fluorescence of THC8 at 420 and 510 nm, respectively, broadened the spectral absorption of the OPV, possibly through Förster resonance energy transfer. In addition, the morphology of the device active layer was improved with the addition of a suitable amount of THC8. Consequently, the charge transport property of the active layer was improved. The best power conversion efficiency (PCE) of the device with THC8 was 3.88%, a 25% increase compared to the PCE of a pristine OPV.

CO2 template synthesis of metal formates with a ReO3 net.

The serendipitous discovery of CO2 as a template in the fabrication of ferric formate (1) has led to the preparation of serial metal(III) formates [MIII(HCOO)3.3/4CO2.1/4H2O.1/4HCOOH ]infinity (M = Fe(1), Al (2), Ga (3), and In(4)). The X-ray single-crystal determinations showed that the metals have octahedral geometries and are linked by HCOO- in the anti-anti style into a 3D ReO3 net, where CO2 molecules exist in cages of mmm symmetry and are hydrogen bonded to the formic CH groups. An X-ray powder diffraction (XRD) study revealed that 2 is identical to the documented [Al(HCOO)3.xH2O]. Further synthetic experiments and 13C NMR spectroscopy eventually confirmed that 2 should be formulated as [Al(HCOO)3.3/4CO2.1/4H2O.1/4HCOOH ]infinity, which for decades had been mistakenly given as [AlIII(HCOO)3.xH2O].