The effect of different surface morphologies obtained by anisotropic etching on the light trapping and short circuit current of single crystalline silicon solar cells was investigated. The anisotropic texturing of a (1 0 0) silicon surface was performed using potassium hydroxide (KOH) solution and/or tetramethylammonium hydroxide (TMAH) solution including isopropyl alcohol (IPA) additive or tertiary butyl alcohol (TBA) additive. Texturing in TMAH solution formed smaller pyramids on the textured surface compared with texturing in KOH solution. Although the textured samples showed similar reflectances (except in the case of the TBA additive), they showed different short circuit currents. Texturing in KOH/TMAH solution led to a 9.6% increase in short circuit current compared with texturing in KOH/IPA solution, a typical etchant in commercial processes. Based on these results, the reflectivity has no simple proportionality relationship to the short circuit current, and the short circuit current of silicon solar cells should be the criterion used in evaluating texturing effects on reducing reflectance and forming a sound junction with high collection efficiency. 相似文献
As part of developmental research for an inquiry-oriented differential equations course, this study investigates the change in students’ beliefs about mathematics. The discourse analysis has identified two different types of perspective modes - i.e., discourse of the third-person perspective and discourse of the first-person perspective - in the students’ mathematical narratives, depending on their ways of positioning themselves with respect to mathematics. In the third-person perspective discourse, the students positioned themselves as passive recipients of mathematics that has been established by some external authority. In the first-person perspective discourse, the students positioned themselves as active mathematical inquirers and produced mathematics by interweaving their own mathematical ideas and experiences. Over the semester, students’ mathematical discourse changed from third-person perspective narratives to first-person perspective narratives. This change in their discourse pattern is interpreted as an indication of change in their beliefs about mathematics. Finally, this article discusses the instructional features that promote the change. 相似文献
Aqueous gold nanorod colloids aggregated by Cl- are further assembled into linearly aligned structures of linear
bundles during evaporation on TEM grids. Gold nanorods in bundles are also
oriented in nearly head-to-tail shapes in the microscopic scale. Induced
dipolar long-range interactions in the mesoscopic scale are suggested to
drive gold nanorods to aggregate. Although surface-plasmon absorption at
transverse resonances decreases, that at longitudinal resonances increases
with aggregation. The photon-thermalized heat of the dispersed and the
aggregated gold nanorods dissipates to immediately surrounding media on the
time scales of 100 and 800 ps, respectively. 相似文献
The purpose of this research was to understand how one teacher reflected on different classroom situations and to understand whether the teacher's approach to these reflections changed over time. For the purposes of this study, we considered reflection as the teacher's act of interpreting her own practices and students' thinking to make sense of student understanding and how teaching might relate to that understanding. We investigated a middle school mathematics teacher's reflection on her students while watching videotapes of her classroom and categorized the reflection as Assess, Interpret, Describe, Justify, and Extend. The results show a higher percentage of Extend instances in later interviews than in earlier ones indicating the teacher's increasing attention to her own teaching in how her students developed their understanding. In addition, her reflection became clearer and better integrated as defined by the Cohen and Ball's triangle of interactions. 相似文献
Synthesis and characterization of ITO nanoparticles were investigated in the present study. To synthesize the ITO nanoparticles flame spray pyrolysis was introduced. The average particle diameter increased with an increase in the molar concentration of the precursor. Raising the maximum flame temperature by controlling the gas flow rates also led to an increase in the average diameter of the particles. The crystalline ITO nanoparticles were synthesized, and their average primary particle diameters ranged from 11 to 20 nm. ITO thin films were prepared with a sol consisted of the ITO nanoparticles and a polymer binder. Effect of average particle diameter of the ITO nanoparticles on the transparency and the surface resistance of the ITO thin films were measured. As the average particle diameter increased, the transparency and the surface resistance decreased from 92 to 83% and from 1.0 × 104 to 0.8 × 104Ω/□, respectively. 相似文献
In the title complex, [Cu(N3)2(C15H26N2)], the Cu atom is surrounded by the two N atoms of the chelating (?)‐α‐isosparteine ligand and another two N atoms from the two azide anions, forming a distorted CuN4 tetrahedron. The two azide anions are terminally bound to the CuII atom, and the dihedral angle between the Nsparteine—Cu—Nsparteine and Nazide—Cu—Nazide planes is 50.0 (2)°. 相似文献
The least-squares meshfree method (LSMFM) for rigid-plasticity based on J2-flow rule and infinitesimal theory is proposed. In the least-squares formulation the squared residuals of the constitutive and equilibrium equations are minimized. Those residuals are represented in a form of first-order differential system using the velocity and stress components as nodal unknowns and thus the proposed formulation is a mixed-type method. Also the penalty scheme for the enforcement of the boundary and frictional contact conditions is devised and the reshaping of nodal supports is introduced to avoid the difficulties due to the severe local deformation near the contact interface. The proposed method does not require any structure of extrinsic cells for the construction of shape functions, the treatment of incompressibility, the integration of variational formulation and the reconstruction of approximation. Through some numerical examples of metal forming processes, the validity and effectiveness of the method are discussed. 相似文献
Metal complexes with Schiff base ligands have been suggested as potential phosphors in electroluminescent devices. In the title complex, tetrakis[6‐methyl‐2‐({[(pyridin‐2‐yl)methyl]imino}methyl)phenolato‐1:2κ8N,N′,O:O;3:2κ8N,N′,O:O]trizinc(II) hexafluoridophosphate methanol monosolvate, [Zn3(C14H13N2O)4](PF6)2·CH3OH, the ZnII cations adopt both six‐ and four‐coordinate geometries involving the N and O atoms of tetradentate 6‐methyl‐2‐({[(pyridin‐2‐yl)methyl]imino}methyl)phenolate ligands. Two terminal ZnII cations adopt distorted octahedral geometries and the central ZnII cation adopts a distorted tetrahedral geometry. The O atoms of the phenolate ligands bridge three ZnII cations, forming a dicationic trinuclear metal cluster. The title complex exhibits a strong emission at 469 nm with a quantum yield of 15.5%. 相似文献
The femtosecond transient absorption (TA) characterization of a new benzothiadiazole (BT)‐based donor–acceptor conjugated copolymer, poly[(2,6‐dithieno[3,2‐b:2′,3′‐d]thiophene)‐alt‐(4,7‐di(4‐octyldodecylthiopen‐2‐yl)‐2,1,3‐benzo[c][1,2,5]thiadiazole (PBT), as well as its fluorinated derivatives, PFBT and PDFBT, is carried out. Additionally, bulk heterojunction (BHJ) films consisting of the copolymers and [6,6]‐phenyl‐C71‐butylic acid methyl ester (PC70BM) are examined using TA spectroscopy. Both the singlet excited state dynamics in the copolymers and the charge transfer state dynamics in the BHJs are investigated in terms of fluorination dependency; the fluorinated copolymers exhibit less singlet exciton recombination rate than the fluorine‐free copolymer, and the BHJs including the fluorinated copolymers display slower monomolecular recombination than the fluorine‐free analogue. Furthermore, the excitation‐intensity‐dependent TA dynamics of the copolymers and BHJs is investigated, revealing that, when sufficiently high excitation intensity is used to induce annihilation processes, the fluorinated copolymers and BHJs incorporating the fluorinated copolymers show more rapid TA decay ascribable to morphological enhancement. These TA spectroscopic findings are found to correlate with the device characteristics with respect to fluorinated content in the polymer solar cells. In particular, both the short‐circuit current density and fill factor of BHJ solar cells correspond closely with the fast decay parameters of the BHJ films under high excitation intensity.