- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Absorption Enhancement of a Thin Silicon Film with a 3D Photonic Band Gap Crystal Back Reflector
摘要： Currently, the efficiency of thin silicon film solar cells is constrained by a limited intrinsic absorption of silicon. The efficiency could be significantly increased by using a highly efficient back reflector that sends unabsorbed light back into the solar cell [1]. As an interesting candidate for a back reflector, we study here a thin 3D photonic band gap crystal [2, 3] that forbids light within the band gap for all directions and for all polarizations. We consider a dispersive complex refractive index obtained from experiments [4]. We find by extensive finite-element computations of the 3D time-harmonic Maxwell equations that even a very thin silicon 3D photonic band gap crystal slab reflects broadband visible light omnidirectionally for all polarizations. Our results show a nearly 2.6 times enhanced angle- and polarization-averaged absorption between 680 nm and 890 nm compared to a 2400 nm thin silicon film. We observe that a 3D inverse woodpile photonic crystal enhances the absorption of a thin silicon film by (i) behaving as a perfect reflector exhibiting nearly 100% reflectivity in the stop bands, and by (ii) generating guided resonant modes at many discrete wavelengths (as illustrated in Figs. 1(a, b)). We find that the absorption is enhanced by positioning an inverse woodpile back reflector at the back side of a thin silicon film, which will keep the length of the solar cell unchanged and also reduce the mass of the thin film solar cell. For a very thin sub-wavelength absorbing layer with a photonic crystal back reflector, as shown in Fig. 1(c), we identify two physical mechanisms that cause the large enhancement at discrete wavelengths: (i) a guided resonance due to the Bragg attenuation length of the photonic crystal [5] and (ii) confinement due to the effective surface defect on the photonic crystal.
关键词： back reflector,thin silicon film,absorption enhancement,3D photonic band gap crystal,solar cells
更新于2025-09-16 10:30:52
-
Analysis of Defects and Surface Roughness on the Hydrogenated Amorphous Silicon (a-Si:H) Intrinsic Thin Film for Solar Cells
摘要： Effect of defect - through observation of energy absorption Urbach, on deposition rate, energy band gap, and surface roughness of intrinsic thin film are investigated using Radio Frequency Plasma Enhance Chemical Vapor Deposition (RF-PECVD). Films are grown on ITO (Indium Tin Oxide) glass substrate. Analysis of energy band gap is conducted to determine changes in the structure of a thin film of a-Si:H. Energy band gap is important to determine the portion of the spectrum of sunlight that is absorbed solar cells. From the characterization using UV-Vis spectrometer and the Tauc’s plot method, the width of the resulting energy band gap is greater if the hydrogen dilution is increased. It can be shown that the increase of the hydrogen dilution, will increase the energy band gap, and the surface roughness of thin layers. Instead, the improvement of the hydrogen dilution decrease the rate of deposition and Urbach energy. It is estimated that with greater hydrogen dilution, an intrinsic thin film of a-Si:H is more conductive for more reduction in residual of band tail defects or dangling bond defects.
关键词： RF-PECVD,a-Si:H,Energy band gap,Urbach energy,Hydrogen dilution
更新于2025-09-16 10:30:52
-
Influence of 2-Amino-4-methylpyridine and 2-Aminopyrimidine Ligands on the Malonic Acid-Cu(II) System: Insights through Supramolecular Interactions and Photoresponse Properties
摘要： Two Cu(II)-malonate complexes with 2-amino-4-methylpyridine (complex 1) and 2-aminopyrimidine (complex 2) auxiliary ligands were synthesized, and their single-crystal X-ray diffraction structures were established. Change in the auxiliary ligand exhibits substantial structural variation in the present complexes. Complex 1 shows a one-dimensional anionic copper-malonate moiety connected by the malonate bridge, whereas complex 2 is a mononuclear one. For both the complexes, auxiliary ligands are attached with the Cu-malonate moiety through various noncovalent interactions. Optical band gap, electrical conductivity, and photosensitivity of complexes 1 and 2 were measured, but the values of electrical parameters of the complexes significantly differ from each other. However, the magnitudes of electrical parameters increase several times for both the complexes when they are exposed under visible light, though the values of light sensing parameters of complex 1 were found to be higher than those of complex 2. Density functional theory calculations for complex 1 were carried out to support the experimental result.
关键词： 2-aminopyrimidine,electrical conductivity,Cu(II)-malonate complexes,density functional theory,2-amino-4-methylpyridine,optical band gap,noncovalent interactions,photosensitivity
更新于2025-09-16 10:30:52
-
From CuFeS <sub/>2</sub> to Ba <sub/>6</sub> Cu <sub/>2</sub> FeGe <sub/>4</sub> S <sub/>16</sub> : rational band gap engineering achieves large second-harmonic-generation together with high laser damage threshold
摘要： A new germanium-based sulfide, Ba6Cu2FeGe4S16, achieves a band-gap broadening of more than 1 eV relative to CuFeS2. Remarkably, Ba6Cu2FeGe4S16 exhibits excellent comprehensive NLO performance (SHG, 1.5 (cid:2) AgGaSe2; LDT, 2 (cid:2) AgGaSe2), satisfying the essential requirements of mid-IR NLO candidates.
关键词： laser damage threshold,mid-IR NLO materials,germanium-based sulfide,second-harmonic-generation,band-gap engineering
更新于2025-09-16 10:30:52
-
Nano-scale sulfurization of the Cu <sub/>2</sub> ZnSnSe <sub/>4</sub> crystal surface for photovoltaic applications
摘要： The objective of this study was to find an effective method to improve VOC without JSC loss for Cu2ZnSnSe4 (CZTSe) monograin layer solar cells. Sulfurization of the surface of the kesterite absorber layer may lead to enhanced device efficiency via band gap widening at the surface. Surface sulfurization was carried out in two steps: a CdS layer was first deposited onto the CZTSe crystals by a chemical solution deposition method, and then the CdS-coated CZTSe was annealed at elevated temperature in evacuated quartz ampoules. The thickness of the sulfurized surface of CZTSe crystals was varied by adjusting the thickness of the CdS layer (from 100 nm to 200 nm) and by modifying the temperature of the annealing process from 400 to 700 °C for 60 min. SEM, EDX and Raman analysis showed that the CdS layer still existed on the surface of CZTSe crystals after annealing at 400 °C. After annealing at higher temperatures, the CdS layer disappeared and a new surface layer was formed. Annealing at 570 °C resulted in secondary phases on the surface, which are probably caused by decomposition reactions on the CZTSe crystal surface. Annealing at 700 °C formed a well-crystallized Cu2ZnSn(S, Se)4 thin layer on the surface of the CZTSe crystals, which was confirmed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The Raman peak located at 331 cm?1 provides strong evidence that a wider band gap Cu2ZnSn(S, Se)4 surface layer is formed after the sulfurization while the CdS peak at 308 cm?1 has disappeared. Compositional profiles of EDX and XPS showed that S is located in the surface layer, but Cd has diffused into the bulk of the crystal and acts as a dopant. The content of S in Cu2ZnSn(S, Se)4 depended on the CdS layer thickness.
关键词： CZTSe,band gap engineering,sulfurization,solar cells,photovoltaic applications
更新于2025-09-16 10:30:52
-
Investigation of the structural, optical, elastic and electrical properties of spinel LiZn <sub/>2</sub> Fe <sub/>3</sub> O <sub/>8</sub> nanoparticles annealed at two distinct temperatures
摘要： Nanoparticles of Li0.5ZnFe1.5O4 (LiZn2Fe3O8) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures. X-ray diffractograms and Rietveld refinement confirmed the formation of the spinel structure. The morphology was analyzed by electron microscopy, which showed that the grains were composed of different crystallites. Elastic properties were determined from infrared spectroscopy. It was found that the elastic parameters increased with the increase in annealing temperatures. The band gap depends on the annealing temperature and it decreased on increasing the particle size. The conductivity of the specimen annealed at 500 °C followed either the Jonscher's model or Drude's model depending on the temperature range. This conductivity decreased when the annealing temperature was raised by 600 °C. AC conductivity was found to be controlled by the hopping model. A single relaxation phenomenon was evidenced for each sample from impedance analysis. The Nyquist diagram proved that the samples were simultaneously capacitive and resistive and also supported the presence of multiple relaxation times.
关键词： annealing temperature,spinel,conductivity,LiZn2Fe3O8,impedance analysis,band gap,elastic properties,sol–gel auto-combustion
更新于2025-09-16 10:30:52
-
Effect of solid-H <sub/>2</sub> S gas reactions on CZTSSe thin film growth and photovoltaic properties of a 12.62% efficiency device
摘要： We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stacked structure and described the phenomenon of Zn elemental volatilization using the MZCT stacked structure. We introduced H2S gas to effectively control the S/(S + Se) ratio of the film in the sulfo-selenization process and to suppress Zn volatilization. Unlike during the selenization process, a stable ZnSSe thin film was formed on the precursor surface during the sulfo-selenization process. The formation of the ZnSSe thin film inhibited Zn volatilization, which facilitated control of the thin film stoichiometry and played an important role in crystal growth. In addition, the sulfo-selenization process using H2S forms a grading of the S/(S + Se) ratio in the depth direction in the ZnSSe layer. The ZnSSe layer with this property causes the band gap grading in the CZTSSe absorption layer. Finally, through our optimized annealing process, we realized a world record CZTSSe solar cell with a certified power conversion efficiency of 12.62% and a centimetre-scale (1.1761 cm2) efficiency of 11.28%.
关键词： CZTSSe,H2S gas,photovoltaic,sulfo-selenization,Zn volatilization,thin film,band gap grading
更新于2025-09-16 10:30:52
-
A Rapid Synthesis of Vertically Aligned Taper-Like K-Doped ZnO Nanostructures to Enhance Dye-Sensitized Solar Cell Efficiency
摘要： Large-scale K-doped ZnO nanotapers were successfully grown on an indium tin oxide (ITO) substrate using a facile electrochemical route. The structural and morphologic analysis exhibited that the K-doped ZnO nanostructures had a nanotaper morphology and strong preferential [0001] c-axis direction with a hexagonal polycrystalline structure. The optical results show that the incorporation of K+ ions as the donors in a ZnO lattice leads to substantial modulation of the band gap structure of ZnO nanotapers, which results in a redshift in the ultraviolet emission peaks. The considerable enhancement of performance in K-doped ZnO-based dye-sensitized solar cells (DSSCs) can be related to the doping structure, which leads to higher dye loading (3.34 9 10(cid:2)8 mol/cm2). The good photovoltaic behavior of the K-doped ZnO nanotapers can be attributed to the higher surface-to-volume ratio and large K-doped ZnO nanotaper/ITO interfacial band bending, indicating the potential of a low-temperature aqueous electrochemical approach to synthesizing doped ZnO nanotapers for DSSCs.
关键词： K-doped ZnO,nanotapers,dye-sensitized solar cells,electrochemical route,band gap modulation
更新于2025-09-16 10:30:52
-
Effect of Potassium Nitrate in ZnO Nanoparticle Synthesis to Study the Performance of Dye Sensitized Solar Cell
摘要： X-ray diffraction, Raman investigations, band gap energy of zinc oxide nanoparticles (ZnO NPs) along with current-voltage characteristic curves of an assembled dye-sensitized solar cell (DSSC) are presented in this article. ZnO NPs were first synthesized with and without potassium nitrate (KNO3) salt by precipitation method from precursor solutions of zinc acetate and sodium hydroxide. Then, their thin films were deposited on FTO substrates from the paste made with acetic-acid glacial, and Triton X-100 in ethanol by doctor blade method. The X-ray diffraction (XRD) pattern of ZnO NPs prepared without KNO3 annealed at 500 °C showed a hexagonal wurtzite structure with preferred orientation along (101) planes and crystallite size of 25 nm. Very similar XRD pattern was found for ZnO NPs prepared with KNO3. The crystallite size was found decreased to 17 nm for ZnO NPs made with KNO3 salt. Raman spectrum of ZnO NPs showed the presence of E2 high or E2(2) peak at 437 cm-1. The optical band gaps of the ZnO thin films prepared from ZnO NPs with and without KNO3 were measured to be of 3.16 eV and 3.26 eV, respectively. After sensitizing the above-prepared ZnO films by dye extract of Artocarpus lakoocha, the dye-sensitized solar cells were prepared, and their performance was tested by measuring I-V curves under light illumination of the power density of 1000 W/m2. The measurement showed highest Isc and Voc of 44 μA and 326 mV, respectively.
关键词： Dye-sensitized solar cell,Band gap energy,ZnO nanoparticles,X-ray diffraction,Raman spectrum
更新于2025-09-16 10:30:52
-
Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications
摘要： Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene (BDT(EH)) and 4,8-bis(octyloxy)-benzo[1,2-b:4,5-b’]dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, Td “349 jC), slightly lower band-gap (Eg “2.10 eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36 eV) level compared to those (Td “336 jC, Eg “2.11 eV, and HOMO “–5.30 eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.
关键词： small molecule solar cells,wide band-gap molecules,quinoxaline-based molecules,benzodithiophene-based molecules,organic solar cells
更新于2025-09-16 10:30:52