Ziyang Hu

Highly efficient organic photovoltaic devices using F-doped SnO2 anodes

Transparent F-doped SnO2 (FTO) is used as an anode material in organic photovoltaics based on poly(3-hexylthiophene) and [6, 6]-phenyl C61-butlyric acid methyl ester. Power conversion efficiency of 4.41% is achieved under 100 mW/cm2 simulated AM 1.5G solar illumination, which is comparable to that (4.25%) of the reference cells fabricated on indium tin oxide (ITO) glass substrates. Our results indicate that FTO anodes are a viable alternative to ITO for photovoltaic devices for cost effective fabrication of organic photovoltaic devices.

Effect of textured electrodes with light-trapping on performance of polymer solar cells

Textured electrodes with rough surface in combination with reflective back contacts provide efficient light-trapping by light scattering and multiple reflections to increase the path length of the light, and the resulting enhanced efficiency of organic photovolatics. In this paper, the effect of textured electrodes with different surface morphology on the performance of polymer solar cells was investigated. Two kinds of textured SnO2:F (FTO) electrodes possessing “V” (V-FTO) and “U” (U-FTO) topography, respectively, were used as the front electrodes of polymer solar cells. Due to the enhanced light absorption in active layer, the resultant cells with U-FTO and V-FTO showed 9% and 6% improvement in short current density (Jsc), respectively, compared with the flat FTO electrode. The U-FTO electrode was amenable to coating a conformal buffer layer and preferred to obtain high efficient cells. However, the enhanced Jsc of the V-FTO cells did not contribute to the improved efficiency for the decreased fill fac...

Efficient polymer solar cells based on light-trapping transparent electrodes

Highly efficient and cost-effective polymer solar cells (PSCs) fabricated on textured fluorine doped transparent conductive (FTO) electrodes are achieved. Such electrodes with rough surface in combination with reflective back contacts provide efficient light-trapping by light scattering and multiple reflections to increase the path length of the light. Due to the increased light absorption in active layer, the resultant PSCs base on polymer:fullerene system show 10% and 8% improvement in short current density and efficiency, respectively, compared with the reference cell based on the flat electrodes.

Indium-Doped Zinc Oxide Thin Films as Effective Anodes of Organic Photovoltaic Devices

Indium-doped zinc oxide (IZO) thin films were prepared by low-cost ultrasonic spray pyrolysis (USP). Both a low resistivity ( cm) and an average direct transmittance ( nm) about 80% of the IZO films were achieved. The IZO films were investigated as anodes in bulk-heterojunction organic photovoltaic (OPV) devices based on poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester. The device fabricated on IZO film-coated glass substrate showed an open circuit voltage of 0.56 V, a short circuit current of 8.49 mA cm−2, a fill factor of 0.40, and a power conversion efficiency of 1.91%, demonstrating that the IZO films prepared by USP technique are promising low In content and transparent electrode candidates of low-cost OPV devices.

Structured light for focusing surface plasmon polaritons

We propose a structureless method for focusing surface plasmon polaritons (SPPs) on a flat metal film under illumination of radially polarized cogwheel-like structured light beams. Without metal structures, the locally induced SPPs can further be propagated following the predefined patterns to form symmetric focal spots with dimensions beyond diffraction limit. Benefiting from the radial polarization, this method can be employed to pattern various center-symmetric evanescent distributions for generating SPPs reconfigurably. The SPPs will be propagating and focusing in radial directions.

Dynamic surface plasmon patterns generated by reconfigurable “cogwheel-shaped” beams

A method for generating and controlling dynamic surface plasmon patterns by highly focused “cogwheel-shaped” beams is studied theoretically and experimentally. The “cogwheel” beams are formed by collinear superposition of two Laguerre–Gaussian beams with equal but opposite topological charges. It is shown that the patterned surface plasmons can be reconfigured locally with advantages over patterned metallic islands.

Apodized waveguide arrays induced by photorefractive nonlinear surface waves

A new type of nonlinear waveguides, photorefractive surface optical waveguides is suggested, which can be induced by photorefractive surface waves on the boundary of photorefractive crystal. The disturbed refractive index distribution of such waveguides behaves as a periodic lattice with apodized envelope, thus we call them photorefractive surface apodized waveguide arrays. Moreover, the dispersion relation and corresponding modes are analyzed. It is very interesting that the dispersion curves of index-guided modes and Bragg-guided modes couple and intertwine with each other, and anti-crossings instead of crossings between them hence generate some mini-gaps. Moreover there exists a type of extraordinary modes constituted by the splice of index-guided modes and Bragg-guided modes.

Regulation of photorefractive surface apodized and chirped waveguide arrays

The tangent-like and sine-like characteristics in the head and tail regions of photorefractive surface waveguide arrays are elaborately demonstrated, and the regulation of such waveguide arrays on the written beam, background illumination, and external electric field is systematically studied for the first time. For the photorefractive surface apodized waveguide arrays, it is observed that guided mode bands of the fundamental mode gradually split and eventually reach saturation as a result of the influence of the power of photorefractive surface waves on the modulation depth of the refractive index; the period can be effectively adjusted by the wavelength and grazing angle of the written beam. However, there is an interesting chirp near surface for a large grazing angle. For the photorefractive surface nonlinearly chirped waveguide arrays, the amplitude, sign, and initial position of chirp can be conveniently regulated by an external electric field, background illumination, and incident beam, etc., and the modulation depth can also be flexibly adjusted by the influence of external electric fields on the refractive index of substrate.