Effect of temperature on tunneling and quantum efficiency in cigs solar cells

Utilizing the two-band approximation and Wentzel-Kramers-B ri l l oui n (WKB) approximation, by including the temperature-dependent effective masses and nonparabolicity effects, an investigation of the temperature dependent band-to-band tunneling process is discussed. In comparison with the parabolic approximation and non- parabolic approximation, the tunneling probability is strongly dependent on the non-parabolicity factor. The temperature dependence of the energy band gap, electron effective mass and light hole effective mass is investigated. The tunneling current density function is derived by a series representation of the incomplete gamma function with non-parabolic effect and its variation at low temperature is also investigated. When the Fermi level of holes is in excess of that of electrons, i.e., EFp\u3e\u3eEFn, the current density function can be successfully simplified as the Fowler-Nordheim formulation. The quantum efficiency model, for CIGS solar cells, is discussed. Device modeling and simulation studies of a Cu(In1-x,Gax)Se2 (CIGS) thin film solar cell are carried out. A variety of graded band-gap structures, including space charge region (SCR) grading, back surface region grading, and double grading of the CIGS absorber layer are considered. A position-dependent absorption coefficient α(x, hv) is obtained by a differential equation for the photon flux φ(x, hv). The quantum efficiency can be calculated by IQE=(φ1-φ2)/φ3. The temperature dependence of the quantum efficiency is also investigated in this thesis

Atomic insights into the oxidative degradation mechanisms of sulfide solid electrolytes

Electrochemical degradation of solid electrolytes is a major roadblock in the development of solid-state batteries. Combining X-ray absorption spectroscopy characterization, first-principles simulations, and machine learning, here we report the atomic-scale oxidative degradation mechanisms of sulfide electrolytes using Li3PS4 (LPS) as a model system. The degradation begins with a decrease of Li neighbor affinity to S atoms, followed by the formation of S-S bonds as the PS4 tetrahedron deforms. After the first cycle, the PS4 motifs become strongly distorted, and PS3 motifs start to form. The distortion of PS4 and the formation of S-S bonds are correlated with an increased interfacial impedance. We identify the spectral fingerprints of the local structural evolution and use them as a proxy for the electrochemical stability of phosphorus sulfide electrolytes, as demonstrated in argyrodite Li6PS5Cl. This study provides guidance for controlling macroscopic reactions through microstructural engineering and can advance the rational design of sulfide electrolytes

Ecological Efficiency Analysis in Zhejiang Province: Based on Improved Super-SBM Model

This paper use the super efficiency SBM-DEA model with undesirable outputs to calculate the ecological efficiency of Zhejiang Province from 2001 to 2018, and construct multiple linear regression model that evaluating the influencing factors of ecological efficiency based on it. The ecological efficiency of Zhejiang Province fluctuated and increased during the study period, which was mainly driven by pure technical efficiency. In the multiple regression analysis, it can be concluded that income factors, structural factors and institutional factors have a gradually weakening positive impact on ecological efficiency. This paper argues that Zhejiang Province should make full use of regional advantages, resource advantages and talent advantages on the basis of maintaining the current industrial level. It is advised to vigorously develop high-tech industries, strengthen international communications on knowledge and seek new economic growth points. Finally a higher level of coordination between economic development and ecological protection can be achieved

Relighting Photosensitizers by Synergistic Integration of Albumin and Perfluorocarbon for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) is hampered by poor water solubility and skin phototoxicity of photosensitizers (PSs). Incorporation of PSs into nanocarrier (Nano-PDT) has been designed to overcome these problems. However, self-quenching of PSs highly condensed in Nano-PDT significantly reduced singlet oxygen (¹O₂) generation, resulting in unsatisfactory PDT efficacy. Here, we developed a novel tripleffect Nano-PDT, which has a special core–shell nanostructure by synergistic integration of perfluorotributylamine (PFTBA) and human serum albumin (HSA) to improve PDT. It has three mechanisms to relight quenched PSs, thereby generating more ¹O₂. First, PSs uniformly dispersed in the shell, preventing self-quenching caused by π–π stacking. Second, HSA as nanocarrier extends the triplet-state lifetimes of PSs, increasing the amount of ¹O₂. Third, PFTBA as core dissolves and protects¹ O₂ to extend the duration time of action of ¹O₂. Compared with PS-encapsulated Nano-PDT, the self-quenching of PSs in tripleffect Nano-PDT can be effectively overcome. The fluorescence and ¹O₂ generation of PS are increased by approximately 100-fold and 15-fold, respectively. After intravenous injection into tumor-bearing mice, the tumor growth is significantly inhibited, while the PS-encapsulated Nano-PDT has almost no effect. The novel tripleffect Nano-PDT may guide improvement of existing clinical PDT and future PDT design

High- Resolution In- Situ Synchrotron X- Ray Studies of Inorganic Perovskite CsPbBr3: New Symmetry Assignments and Structural Phase Transitions

Perovskite photovoltaic ABX3 systems are being studied due to their high energy- conversion efficiencies with current emphasis placed on pure inorganic systems. In this work, synchrotron single- crystal diffraction measurements combined with second harmonic generation measurements reveal the absence of inversion symmetry below room temperature in CsPbBr3. Local structural analysis by pair distribution function and X- ray absorption fine structure methods are performed to ascertain the local ordering, atomic pair correlations, and phase evolution in a broad range of temperatures. The currently accepted space group assignments for CsPbBr3 are found to be incorrect in a manner that profoundly impacts physical properties. New assignments are obtained for the bulk structure: Im3¯ (above - 410 K), P21/m (between - 300 K and - 410 K), and the polar group Pm (below - 300 K), respectively. The newly observed structural distortions exist in the bulk structure consistent with the expectation of previous photoluminescence and Raman measurements. High- pressure measurements reveal multiple low- pressure phases, one of which exists as a metastable phase at ambient pressure. This work should help guide research in the perovskite photovoltaic community to better control the structure under operational conditions and further improve transport and optical properties.Examination of single- crystal X- ray diffraction images between - 500 and - 100 K yields new symmetry assignments for CsPbBr3. The space groups are: Im- 3 above - 410 K, P21/m between - 410 K and - 300 K, and Pm below - 300 K. A unit cell volume of - 2ap à 2ap à 2ap is maintained. Local structural measurements reveal non- centrosymmetric short- range order above 300 K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/170301/1/advs2842-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/170301/2/advs2842.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/170301/3/advs2842_am.pd

High-Pressure Synthesis and Ferrimagnetism of Ni3TeO6-Type Mn2ScMO6 (M = Nb, Ta)

The corundum-related oxides Mn2ScNbO6 and Mn2ScTaO6 were synthesized at high pressure and high temperature (6 GPa and 1475 K). Analysis of the synchrotron powder X-ray diffraction shows that Mn2ScNbO6 and Mn2ScTaO6 crystallize in Ni3TeO6-type noncentrosymmetric crystal structures with space group R3. The asymmetric crystal structure was confirmed by second harmonic generation measurement. X-ray absorption near-edge spectroscopies indicate formal valence states of Mn(2+)2Sc(3+)4-Nb5+O6 and Mn(2+)2Sc(3+)Ta(5+)O(6), also supported by the calculated bond valence sums. Both samples are electrically insulating. Magnetic measurements indicate that Mn2ScNbO6 and Mn2ScTaO6 order ferrimagnetically at 53 and 50 K, respectively, and Mn2ScTaO6 is found to have a field-induced magnetic transition