Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.
Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.
In this Letter, we investigate the feasibility of focusing relativistic laser pulses toward diffraction limit by near-critical density plasma lenses. A theoretical model is developed to estimate the focal length of the plasma lens. Particle-in-cell simulations with various pulse parameters, such as pulse duration, beam waist, and intensity, are performed to show the robustness of plasma lenses. The results prove that the near-critical density plasma lenses can be deployed to obtain higher laser peak intensities with sub-wavelength focal spots in experiments.
The aim of this review article is to introduce recent studies on an emergent class of singlet oxygen photosensitizers of potential applications to the photodynamic therapy, with a primary focus on the cyclometalated transition-metal complexes. Singlet oxygen photosensitization performances of various cyclometalated Ir and Pt scaffolds are reviewed, and the general photo-physical properties of relevant systems and the mechanisms of singlet oxygen production via photo-sensitization are also briefly discussed. Thus far, investigations of singlet oxygen sensitization by such Ir and Pt complexes are mainly carried out in organic solvents and under non-physiological conditions, while some research efforts have been made at examining the feasibility of applying pertinent cyclometalated complexes to photodynamic therapy.
A new micromechanics method is proposed to investigate the effective properties of saturated porous media with connected pores. This topic is seldom discussed in the literature because it is difficult to describe the connected pores and skeleton using conventional micromechanics methods. A new micromechanics model (i.e., Model I) is suggested to characterize such saturated porous media in which the pores saturated by fluid are taken as the matrix, and the interconnected randomly oriented long fiber (ROLF)-like solid skeleton is taken as the inclusions. The proposed model is verified by numerical simulations; the simulation results indicate that the difference of the elastic constants calculated for media with interconnected pores and for those with dispersed ROLF solid inclusions is small. Thus, the elastic moduli of Model I can be treated as approximate values for porous media with connected pores. Further, a modified Eshelby tensor for spherical inclusions is derived based on the equivalency of the elastic moduli of Model I and a conventional micromechanics model in which spherical fluid inclusions are distributed randomly in a solid matrix. By means of the modified Eshelby tenor, conventional micromechanics methods can be utilized directly to calculate the effective mechanical and thermal properties of saturated porous media with interconnected pores. Some examples are presented to show that the macroscopic elastic moduli predicted by the proposed method are in good agreement with test data found in the literature.
A new micromechanics method is proposed to investigate the effective properties of saturated porous media with connected pores. This topic is seldom discussed in the literature because it is difficult to describe the connected pores and skeleton using conventional micromechanics methods. A new micromechanics model (i.e., Model I) is suggested to characterize such saturated porous media in which the pores saturated by fluid are taken as the matrix, and the interconnected randomly oriented long fiber (ROLF)-like solid skeleton is taken as the inclusions. The proposed model is verified by numerical simulations; the simulation results indicate that the difference of the elastic constants calculated for media with interconnected pores and for those with dispersed ROLF solid inclusions is small. Thus, the elastic moduli of Model I can be treated as approximate values for porous media with connected pores. Further, a modified Eshelby tensor for spherical inclusions is derived based on the equivalency of the elastic moduli of Model I and a conventional micromechanics model in which spherical fluid inclusions are distributed randomly in a solid matrix. By means of the modified Eshelby tenor, conventional micromechanics methods can be utilized directly to calculate the effective mechanical and thermal properties of saturated porous media with interconnected pores. Some examples are presented to show that the macroscopic elastic moduli predicted by the proposed method are in good agreement with test data found in the literature.
In this paper, one novel qualitative criterion, the bubble break-up (BBU), and two new quantitative criteria, the bubble-rising height (BRH) and bubble-rising velocity (BRV), are proposed and studied to determine the minimum miscibility pressures (MMPs) with the rising-bubble apparatus (RBA). Two respective series of pure and impure CO2-bubble tests in a light crude oil are conducted at six different test pressures and the actual reservoir temperature of Tres=53.0°C. First, the MMPs of the light crude oil–pure and impure CO2 systems are estimated and compared by using four existing (i.e., the bubble shape, size, colour, and rising height) and BBU qualitative criteria. Second, the BRH and BRV quantitative criteria are used to determine the MMPs of the light crude oil–pure CO2 system, in comparison with those from the coreflood tests and vanishing interfacial tension (VIT) technique. Third, these two new quantitative criteria are also applied to determine the MMPs of the light crude oil–impure CO2 (74.87mol.% CO2+25.13mol.% CH4) system and compare them with that from the VIT technique. It is found that the BBU criterion is consistent with the four existing qualitative criteria for estimating the MMPs. By means of the BRH and BRV criteria, two respective MMP ranges of the light crude oil–pure and impure CO2 systems are found to be 11.7–12.4MPa and 23.4–23.5MPa at Tres=53.0°C. Such determined MMPs with the RBA are slightly lower than those from the coreflood tests for the light crude oil–pure CO2 system but relatively higher than those from the VIT technique for the two respective light crude oil–CO2 systems. The newly developed BRH and BRV quantitative technical criteria, plus the novel BBU qualitative technical criterion, can be used to objectively and accurately determine the MMPs with the RBA.
A novel hetero-polycyclic aromatic compound manifesting strong near-infrared (NIR) absorption as well as high-performance n-type semiconducting properties is developed. With an exceptionally low LUMO level at -4.7 eV, this NIR dye (lambda(max) approximate to 1100 nm, epsilon approximate to 105 mol(-1) L cm(-1)) exhibits adequate stability under ambient conditions, with electron mobility up to 0.96 cm(2) V-1 s(-1) measured in solution-processed organic field-effect transistors. A special metal-free C-C coupling serves as a pivotal step in constructing the polycyclic pi-framework of this low-bandgap chromophore, by fusing an electron-deficient naphthalenediimide moiety with an electron-donating naphthalenediamine. Such a rare combination of extraordinary optical and semiconductive attributes is quite valuable for organic small molecules, and promising for unique applications in the opto-electronic field.