This PDF file contains the front matter associated with SPIE Proceedings Volume 8312, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The continuity and Poisson equations are solved numerically to obtain J-V characteristics and photoconversion efficiency of a two-junction solar cell. The cell consists of a top junction comprised of nanowires with bandgap of 1.7 eV grown on a bottom junction comprised of a Si substrate. The lattice relaxation possible in nanowires permits latticemismatched III-V material growth on Si, thereby achieving the optimum bandgaps in a two-junction cell. The model indicates a limiting efficiency of 42.3% under a concentration of 500 Suns (AM1.5D spectrum). This limiting efficiency is similar to that calculated for the planar lattice-matched triple-junction Ge/InGaAs/InGaP cell. Methods of fabricating the nanowire/Si cell are discussed including requirements for nanowire sidewall surface passivation.

The relationship between structure and electronic properties of n-type doped hydrogenated amorphous silicon (a-Si:H) thin films was investigated. Samples with different features were prepared by plasma enhanced chemical vapor deposition (PECVD) at various substrate temperatures. Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to evaluate the structural evolution, meanwhile, electronic-spin resonance (ESR) and optical measurement were applied to explore the electronic properties of P-doped a-Si:H thin films. Results reveal that the changes in materials structure affect directly the electronic properties and the doping efficiency of dopant.

In this paper, we present the integration of an absorbing photonic crystal within a thin film photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning the epitaxial crystalline silicon active layer as a 1D and 2D photonic crystal enabled to increase its integrated absorption by 37%_abs and 68%_absbetween 300 nm and 1100 nm, compared to a similar but unpatterned stack. In order to fabricate such promising cells, a specific fabrication processes based on holographic lithography, inductively coupled plasma etching and reactive ion etching has been developed and implemented to obtain ultrathin patterned solar cells.

The plasmonic enhanced absorption for thin film solar cells with silver nanoparticles (NPs) deposited on top of the amorphous silicon film (a-Si:H) solar cells and embedded inside the active layer of organic solar cells (OSCs) has been simulated and analyzed. Obvious optical absorption enhancement is obtained not only at vertical incidence but also at oblique incidence. By properly adjusting the period and size of NPs, an increased absorption enhancement of about 120% and 140% is obtained for a-Si:H solar cells and OSCs, respectively.

ITO-free organic photovoltaic (OPV) devices with all solution processed transparent anodes of PEDOT:PSS/inkjet printed Ag grid were demonstrated. Through process control, the polymer/metal grid hybrid electrode films are of transparency close to 80% and sheet resistance of 48 ohms/sq. A power efficiency of 1.73% was achieved for the OPV device. The performance can be further improved by process optimization. The technology shows great potential for low-cost manufacturing of OPV solar cells.

In this paper a Xenon-lamp-pumped four rods pulsed Nd:YAG laser is presented. The influence of offset angle of Nd:YAG rods and thermal stable regions in the resonator have been analyzed theoretically, and tolerance of offset angle and is given. A plane-plane symmetrical resonator has been used in the experiment, and the distance between two neighbor rods is two times of that between the mirrors and rods. While input electric power is 58 kW and the duty cycle is 17%, an output laser with an average power of 2026 W, a peak power of 11.9 kW, maximum single pulse energy of 60 J and a beam parameters product of 24.5 mm×mrad has been obtained. The electro-optical conversion efficiency is 3.49 %, and instability of the laser is less than 2 %.

Highly efficient InGaN-base light emitting diodes are crucial for next generation solid state lighting. However, drawbacks in substrate materials such as lattice and thermal expansion coefficient mismatches hold back the lamination efficiency improvement. In the past, patterned sapphire sustrate (PSS) has been proven to be effect to enhance the LED's performance. In this work, we reviewed several promising nano-scale technologies which successfully increase the output of LED through better material quality and light extraction. First, we presented a study of high-performance blue emission GaN LEDs using GaN nanopillars (NPs). It exhibits smaller blue shift in electroluminescent peak wavelength and great enhancement of the light output (70% at 20 mA) compared with the conventional LEDs. Secondly, GaN based LEDs with nano-hole patterned sapphire (NHPSS) by nano-imprint lithography are fabricated structure grown on sapphire substrate. At an injection current of 20mA, the LED with NHPSS increased the light output power of LEDs by 1.33 times, and the wall-plug efficiency is 30% higher at 20mA indicating that it had larger light extraction efficiency (LEE). Finally, we fabricated the high performance electrical pumping GaN-based semipolar {10-11} nano-pyramid LEDs on c-plane sapphire substrate by selective area epitaxy (SAE). The emission wavelength only blue-shifted about 5nm as we increased the forward current from 40 to 200mA, and the quantum confine stark effect (QCSE) had been remarkably suppressed on semipolar surface at long emission wavelength region. These results manifest the promising role of novel nanotechnology in the future III-nitride light emitters.

Light sources with low color temperature (CT) are essential for their markedly less suppression effect on the secretion of melatonin, and high power efficiency is crucial for energy-saving. To provide visual comfort, the light source should also have a reasonably high color rendering index (CRI). In this report, we demonstrate the design and fabrication of low CT and high efficiency organic light-emitting diodes. The best resultant device exhibits a CT of 1,880 K, much lower than that of incandescent bulbs (2,000-2,500 K) and even as low as that of candles, (1,800-2,000 K), a beyond theoretical limit external quantum efficiency 22.7 %, and 36.0 lm/W at 100 cd/m ². The high efficiency of the proposed device may be attributed to its interlayer, which helps effectively distribute the entering carriers into the available recombination zones.

The influence of phosphor sedimentation on the white light-emitting diode with different structure chip was investigated. The phosphor sedimentation phenomenon occurred seriously as encapsulant viscosity lowers. The influence of phosphor sedimentation on the white light-emitting diode with the vertical structure chip whose one side only emits is larger than that of lateral structure chip whose all sides emit. Hence, Difference in luminous efficacy by the phosphor sedimentation reached about 20 % in the case with the vertical structure chip due to optical loss stemmed from the phosphor sediment layer.

We report that crystalline Si thin film solar cells' short circuit current can be significantly enhanced via the incorporation of the rationally-designed Si nanopillar (SiNP) array textured surface. This work points out the potential of the aforementioned cell structure in boosting the performance of Si thin film based solar cells while maintaining the low costs without using high grade raw materials. Except the device performance projection, the underlying physics responsible is also clarified.

As the most efficient thin film solar cells, Cu(InGa)Se₂ based solar cell has attracted extensive studies recently. In this paper we have briefly reviewed recent progress of CIGS solar cells both in the laboratory and in the industry. For the research status, we focused on recent progress in cell structure and material selection/preparation for different functional layers in the highly efficient CIGS solar cells. We also summarized the main achievements from several leading research groups in producing high efficiency CIGS solar cells and presented their efficiency records on different substrates (glass, stainless steel, Ti and polymer). For CIGS industrialization, we reviewed the main progress in several representative CIGS companies. We summarized the fabrication technology and characteristics, and the main achievements in the production capacity for many CIGS companies worldwide. We also reviewed the research progress of our group (CUHK and SIAT) on small size CIGS solar cells and mini-modules. We believe that the CIGS production capacity and actual production will increase very fast and play important role in photovoltaic industry in the near future.

Hexa-peri-hexabenzocoronene (HBC) is a disc-shaped polycyclic aromatic hydrocarbon with remarkable self-association properties. Solution processable alkyl substituted HBC compounds often exhibit discotic liquid crystalline behavior and have been shown to carry charges efficiently in bulk. In recent years, fluorenyl HBC (FHBC) compounds have emerged as promising materials for organic photovoltaics. The fluorene substituent imparts solution processability while maintaining good charge transport characteristics. Power conversion efficiency close to 3% has been reported for organic solar cell devices containing FHBC materials.

Hydrogenated amorphous silicon-germanium (a-SiGe:H) alloy thin films were fabricated by conventional radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) with a gas mixture of silane (SiH4) and germane (GeH4). The structural, optical and electrical properties of the films with different gas volume fraction of germane were investigated by Raman and Fourier transform infrared (FTIR) spectroscopy, ultraviolet and visible (UV-vis) spectroscopy and I-V curves, respectively. The amorphous network and structural disorder in the a-SiGe:H thin films were evaluated by Raman spectroscopy. Meanwhile, the Si-H and Ge-H configurations of the films were investigated by FTIR spectroscopy. From UV-vis spectroscopy and I-V curves, the optical and electrical properties of the testing films could be deduced with varied germanium. It can be concluded that the structural and photoelectronic properties of a-SiGe:H thin films can be influenced apparently by varing of GeH4/(SiH4+ GeH4) ratio in PECVD process.

A 30-mm-length YVO₄/Nd:YVO₄/ YVO₄ composite crystal was used as self-Raman gain material. Yellow radiation at 587 nm was obtained by utilizing a 15-mm-length LBO as frequency-doubling crystal. The maximum average power at 587 nm is up to 8.05 W at the pulse repetition rate of 50 kHz and the pump power of 65 W, with the corresponding optical conversion efficiency of 12.38%. The shortest pulse width, the highest peak power and the maximum pulse energy were measured to be 5.57 ns, 22.1 kW, and 161 μJ, respectively.

Silver nanoparticles have been found many interesting applications, such as absorption amplifiers in dye-sensitized solar cells. However, silver nanoparticles are easily oxidized. In order to protect silver nanoparticles, atomic layers of TiO₂were deposited onto silver nanoparticles coated to a glass slide. Then the glass slide was exposed to corrosive I^-/I₃^- solutions, and the degree of silver etching was measured via scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy (UVS). It was found that 3 nm (30 cycles) of Al₂O₃ with 9 nm of (90 cycles) TiO₂ could completely protect silver nanoparticles from oxidization.

Optical enhancement of organic solar cells with rectangular metallic gratings as the back contact has been investigated numerically. It is demonstrated that a strongly increased light absorption up to 37% with the plasmonic enhanced effect of metallic gratings has been obtained. In addition, we study the light absorption enhancement at oblique incidence and also get a high absorption enhancement within the incident angle of 30 degree.