Search results for "efficiency"
showing 10 items of 1430 documents
First InGaN/GaN thin Film LED using SiCOI engineered substrate
2006
InGaN / GaN multiple quantum well (MQW) light emitting diodes (LEDs) were deposited by metal-organic chemical vapor deposition (MOCVD) onto SiCOI engineered substrates. SiCOI substrates are composed of SiC thin film transferred on a silicon substrate through silicon oxide layer by the Smart Cut™ technology. LEDs structures grown on SiCOI were characterized, then transferred onto Si substrates via a metallic bonding process and SiCOI substrates were removed. Three different metallic stacks were used for metallic bonding, including mirror and barrier diffusion. Vertical thin film LED obtained were characterized and showed a 2 to 3 times increase of external quantum efficiency. These results d…
Photoconductivity and optical properties of silicon coated by thin TiO2 film in situ doped by Au nanoparticles
2013
Light trapping enhancement by plasmonic-active metal nanoparticles (NPs) is believed to be a promising approach to increase silicon-based solar cell efficiency. Therefore, we investigated TiO2 films in situ doped by Au NPs (TiO2:AuNPs) deposited by spin coating on a silicon substrate. Photoconductivity and optical properties of the TiO2:AuNPs/Si structures were studied in comparison with those of TiO2/Si reference samples. We found that an introduction of the 40–50 nm diameter AuNPs into the antireflective TiO2 layer deteriorates the antireflection properties and decreases the external yield of photogeneration of charge carriers. This is due to an increase of the layer reflection in the red…
Efficiency comparison between SiC- and Si-based active neutral-point clamped converters
2015
This paper presents an efficiency comparison between silicon-carbide technology and silicon technology. In order to achieve this, the efficiency of an active neutral-point clamped converter built up with silicon carbide power-devices is compared with the efficiency of an active neutral-point clamped converter built up with silicon power-devices, under a particular operating mode and a particular selection of devices. Firstly, overall losses of both converters are estimated. Then, experimental tests are carried out to measure their overall losses and efficiency. Finally, experimental results are compared with the estimations to support the analysis. The efficiency of the SiC converter is hig…
Investigations of As-S-Se thin films for use as inorganic photoresist for digital image-matrix holography
2011
AbstractAs-S-Se chalcogenide thin films are successfully employed in classical and dot-matrix holography as inorganic photoresists for obtaining a relief-phase hologram. However using these films for image-matrix hologram recording has not been studied due to some features of image-matrix technology. For the applied research of the optical properties of As-S-Se films an experimental device of digital image-matrix holographic recording based on 100 mW 405 nm semi-conductor laser and Spatial Light Modulator (SLM) has been created. The device has the following main parameters: 140 × 105 µm frame size; laser intensity during exposure 10 W/cm2. With the help of this device diffraction grating an…
Modelling and analysis of the influence of solar spectrum on the efficiency of photovoltaic modules
2021
Abstract The article presents the influence of changes in the solar radiation spectrum distribution on the properties of various photovoltaic modules, with particular emphasis on the scattered component. We compared the relative efficiency of the photovoltaic modules based on various semiconductor absorbers during bright and sunny, and cloudy summer days. Additionally, we presented the impact of the module tilt angle on the magnitude of the surface incident scattered component and on the efficiency of the module. The solar spectra for various weather conditions were estimated using specialised computer programmes,such as SolarSpectrum or SMARTS2, and we present here the validation results f…
Photophysical and electroluminescence properties of bis(2′,6′-difluoro-2,3′-bipyridinato-N,C4′)iridium(picolinate) complexes: effect of electron-with…
2015
Herein, we have synthesized a series of 2′,6′-difluoro-2,3′-bipyridine cyclometalating ligands by substituting electron-withdrawing (–CHO, –CF3, and –CN) and electron-donating (–OMe and –NMe2) groups at the 4′ position of the pyridyl moiety and utilized them for the construction of five new iridium(III) complexes (Ir1–Ir5) in the presence of picolinate as an ancillary ligand. The photophysical properties of the developed iridium(III) compounds were investigated with a view to understand the substituent effects. The strong electron-withdrawing (–CN) group containing the iridium(III) compound (Ir3) exhibits highly efficient genuine green phosphorescence (λmax = 508 nm) at room temperature in …
Optimized blue light generation in optically contacted walk-off compensated RbTiOAsO4 and KTiOP1−yAsyO4
1999
Abstract We study type II 1.32 μm second harmonic generation (SHG) in a RbTiOAsO 4 optically contacted walk-off compensated device. The reduction of the effective walk-off angle by a factor of 3.7 with respect to KTiOPO 4 for the same interaction leads to an enhancement by a factor of 10 of the conversion efficiency. A model is proposed for both type I and type II SHG in such a structure. The angular tuning curve is a multi-peaked one, as predicted by the model. The enhancement of the SHG conversion efficiency allows us to optimize the generation of blue laser light at 440 nm: a specially designed KTiOP 0.98 As 0.02 O 4 solid solution crystal achieves angular non-critical phase matching at …
Highly Efficient Thermally Co-evaporated Perovskite Solar Cells and Mini-modules
2020
The rapid improvement in the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has prompted interest in bringing the technology toward commercialization. Capitalizing on existing industrial processes facilitates the transition from laboratory to production lines. In this work, we prove the scalability of thermally co-evaporated MAPbI3 layers in PSCs and mini-modules. With a combined strategy of active layer engineering, interfacial optimization, surface treatments, and light management, we demonstrate PSCs (0.16 cm2 active area) and mini-modules (21 cm2 active area) achieving record PCEs of 20.28% and 18.13%, respectively. Un-encapsulated PSCs retained ∼90% of their initial…
Improvement of DSSC performance by voltage stress application
2016
Dye-sensitized solar cells (DSSCs) are promising third generation photovoltaic devices given their potential low cost and high efficiency. Some factors still affect DSSCs performance, such structure of electrodes, electrolyte compositions, nature of the sensitizers, power conversion efficiency, long-term stability, etc. In this work we discuss the effect of electrical stresses, which allow to improve DSSC performance. We have investigated the outcomes of forward and reverse DC bias stress as a function of time, voltage, and illumination level in the DSSCs sensitized with the N719, Ruthenium complex based dye. We demonstrate that all the major solar cell parameters, i.e., open circuit voltag…
Comprehensive defect suppression in perovskite nanocrystals for high-efficiency light-emitting diodes
2021
Electroluminescence efficiencies of metal halide perovskite nanocrystals (PNCs) are limited by a lack of material strategies that can both suppress the formation of defects and enhance the charge carrier confinement. Here we report a one-dopant alloying strategy that generates smaller, monodisperse colloidal particles (confining electrons and holes, and boosting radiative recombination) with fewer surface defects (reducing non-radiative recombination). Doping of guanidinium into formamidinium lead bromide PNCs yields limited bulk solubility while creating an entropy-stabilized phase in the PNCs and leading to smaller PNCs with more carrier confinement. The extra guanidinium segregates to th…