Wen-Jeng Ho

A Full-Duplex Radio-Over-Fiber Transport System Based on FP Laser Diode With OBPF and Optical Circulator With Fiber Bragg Grating

A full-duplex radio-over-fiber transport system based on an Fabry-Perot laser diode (FP LD) with an optical bandpass filter at the central station, as well as employing an optical circulator with a fiber Bragg grating at the base station, is proposed and demonstrated. Good transmission performances estimated by bit-error rate and eye diagram are obtained in our proposed systems. Since our proposed systems use only an FP LD as a light source for both down-link and up-link transmissions, it reveals a prominent alternative with advantages in simplicity and cost.

Performance-Enhanced Textured Silicon Solar Cells Based on Plasmonic Light Scattering Using Silver and Indium Nanoparticles

Performances of textured crystalline-silicon (c-Si) solar cells enhanced by silver nanoparticles (Ag-NPs) and indium nanoparticles (In-NPs) plasmonic effects are experimentally demonstrated and compared. Plasmonic nanoparticles integrated into textured c-Si solar cells can further increase the absorption and enhance the short-circuit current density (Jsc) of the solar cell. To examine the profile of the proposed metallic particles, the average diameter and coverage of the In-NPs (Ag-NPs) at 17.7 nm (19.07 nm) and 30.5% (35.1%), respectively, were obtained using scanning electron microscopy. Optical reflectance and external quantum efficiency response were used to measure plasmonic light scattering at various wavelengths. Compared to a bare reference cell, the application of In-NPs increased the Jsc of the cells by 8.64% (from 30.32 to 32.94 mA/cm2), whereas the application of Ag-NPs led to an increase of 4.71% (from 30.32 to 31.75 mA/cm2). The conversion efficiency of cells with embedded In-NPs (14.85%) exceeded that of cells with embedded Ag-NPs (14.32%), which can be attributed to the broadband plasmonic light scattering of the In-NPs.

Novel ROF/FTTX/CATV hybrid three-band transport system.

A novel cost-effective radio-over-fiber (ROF)/fiber-to-the-X (FTTX)/CATV hybrid three-band transport system based on direct modulation of a distributed feedback laser diode (DFB LD) with multi-wavelength output characteristic is proposed and experimentally demonstrated. Radio-frequency (RF) (1.25 Gbps/6 GHz) signal with direct modulation, as well as baseband (BB) (622 Mbps) and CATV (channels 2-78) signals with external remodulation are successfully transmitted simultaneously. Low bit error rate (BER) and clear eye diagram were achieved for ROF and FTTX applications; as well as good performances of carrier-to-noise ratio (CNR), composite second-order (CSO) and composite triple beat (CTB) were obtained for CATV signals over an 80-km single-mode fiber (SMF) transport.

Light-trapping performance of silicon thin-film plasmonics solar cells based on indium nanoparticles and various TiO2 space layer thicknesses

Thin-film solar cells have the potential to substantially reduce the material cost of photovoltaic devices. However, to increase the amount of light absorbed in the thin active layer, light trapping is a critical concern in developing thin-film solar cells. In this study, we investigated the suitability of using localized surface plasmons of indium nanoparticles (In NPs) on TiO2 space layers of various thicknesses to enhance the absorption of silicon (Si) thin-film solar cells. The experimental results demonstrated how the combined effects of the incident light plasmonics scattering, surface passivation, and antireflection of In NPs affect the photovoltaic performance of the TiO2 space layer. The optical reflectance, dark current, photocurrent, and external quantum efficiency were measured and compared. Compared with bare-type Si thin-film solar cells, the proposed cells with In NPs on a 59.5-nm-thick TiO2 space layer demonstrated a short-circuit current enhancement of 45.7% (from 2.56 to 3.73 mA) and a conversion efficiency enhancement of 36.2% (from 7.56 to 10.3%).

Photovoltaic Performance Characterization of Textured Silicon Solar Cells Using Luminescent Down-Shifting Eu-Doped Phosphor Particles of Various Dimensions

This paper reports on efforts to enhance the photovoltaic performance of textured silicon solar cells through the application of a layer of Eu-doped silicate phosphor with particles of various dimensions using the spin-on film technique. We examined the surface profile and dimensions of the Eu-doped phosphors in the silicate layer using optical microscopy with J-image software. Optical reflectance, photoluminescence, and external quantum efficiency were used to characterize the luminescent downshifting (LDS) and light scattering of the Eu-doped silicate phosphor layer. Current density-voltage curves under AM 1.5G simulation were used to confirm the contribution of LDS and light scattering produced by phosphor particles of various dimensions. Experiment results reveal that smaller phosphor particles have a more pronounced effect on LDS and a slight shading of incident light. The application of small Eu-doped phosphor particles increased the conversion efficiency by 9.2% (from 12.56% to 13.86%), far exceeding the 5.6% improvement (from 12.54% to 13.32%) achieved by applying a 250 nm layer of SiO2 and the 4.5% improvement (from 12.37% to 12.98%) observed in cells with large Eu-doped phosphor particles.

Electrical and optical performance of plasmonic silicon solar cells based on light scattering of silver and indium nanoparticles in matrix-combination.

This study demonstrates the efficacy of combining a matrix of silver nanoparticles (Ag-NPs) with indium nanoparticles (In-NPs) to improve the electric and optical performance of plasmonic silicon solar cells. We examined the excitation of localized surface plasmons of Ag-NPs and In-NPs using surface enhanced Raman scattering measurements. Optical reflectance and external quantum efficiency (EQE) measurements demonstrate that the light scattering of Ag-NPs at short wavelengths can be improved by surrounding them with In-NPs. This also leads to high EQE band matching in the high energy band of the AM1.5G solar energy spectrum. Impressive improvements in optical reflectance and EQE response were also observed at short wavelengths. Cells with a matrix of Ag-NPs (20% surface coverage) surrounded by In-NPs (80% surface coverage) increased the overall efficiency of the cell by 31.83%, as confirmed by photovoltaic current density-voltage characterization under AM 1.5 G illumination.

A Bidirectional WDM Transport System Based on RSOAs and Optoelectronic Feedback Technique

Abstract-A bidirectional wavelength-division-multiplexing (WDM) transport system base on two reflective semiconductor optical amplifiers (RSOAs) and optoelectronic feedback technique is proposed and experimentally demonstrated. One RSOA is employed as a broadband light source and another RSOA in combination with optoelectronic feedback technique is used as wavelengths reuse and data signal remodulation scheme. System architecture is further simplified by using only one RSOA at the optical node, and system performance is further improved by optoelectronic feedback technique. Impressive performances of bit error rate (BER) (<;10-9) were achieved for both 2.5 Gbps down-link and 1.25 Gbps up-link transmissions.

Enhancing Photovoltaic Performance Using Broadband Luminescent Down-Shifting by Combining Multiple Species of Eu-Doped Silicate Phosphors

This paper demonstrates the application of a broadband luminescent downshifting (LDS) layer with multiple species of europium (Eu)-doped silicate phosphors using spin-on film technique to enhance the photovoltaic efficiency of crystalline silicon solar cells. The surface morphology of the deposited layer was examined using a scanning electron microscope (SEM). The chemical composition of the Eu-doped silicate phosphors was analyzed using energy-dispersive X-ray spectroscopy (EDS). The fluorescence emission of the Eu-doped silicate phosphors was characterized using photoluminescence (PL) measurements at room temperature. We also compared the optical reflectance and external quantum efficiency (EQE) response of cells with combinations of various Eu-doped phosphors species. The cell coated with two species of Eu-doped phosphors achieved a conversion efficiency enhancement (∆η) of 19.39%, far exceeding the ∆η = 15.08% of the cell with one species of Eu-doped phosphors and the ∆η = 8.51% of the reference cell with the same silicate layer without Eu-doped phosphors.

Electrical and Optical Characterization of Sputtered Silicon Dioxide, Indium Tin Oxide, and Silicon Dioxide/Indium Tin Oxide Antireflection Coating on Single-Junction GaAs Solar Cells

This study characterized the electrical and optical properties of single-junction GaAs solar cells coated with antireflective layers of silicon dioxide (SiO2), indium tin oxide (ITO), and a hybrid layer of SiO2/ITO applied using Radio frequency (RF) sputtering. The conductivity and transparency of the ITO film were characterized prior to application on GaAs cells. Reverse saturation-current and ideality factor were used to evaluate the passivation performance of the various coatings on GaAs solar cells. Optical reflectance and external quantum efficiency response were used to evaluate the antireflective performance of the coatings. Photovoltaic current-voltage measurements were used to confirm the efficiency enhancement obtained by the presence of the anti-reflective coatings. The conversion efficiency of the GaAs cells with an ITO antireflective coating (23.52%) exceeded that of cells with a SiO2 antireflective coating (21.92%). Due to lower series resistance and higher short-circuit current-density, the carrier collection of the GaAs cell with ITO coating exceeded that of the cell with a SiO2/ITO coating.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively.