- 标题
- 摘要
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- 实验方案
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π-Conjugated small molecules enable efficient perovskite growth and charge-extraction for high-performance photovoltaic devices
摘要： A π-conjugated small molecule N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) is introduced into a poly (bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) hole transport layer in inverted perovskite solar cells (PSCs). The NPB doping induces better perovskite crystal growth owing to a strong π-π interaction with PTAA and cation-π interactions with CH3NH3+ (MA+). In addition, NPB doping not only improves the wettability of PTAA and regulates the perovskite crystallization to achieve a larger grain size, but also moves the valence band energy of the hole transport layer closer to the perovskite layer. Consequently, the fabricated PSCs delivered a power conversion efficiency (PCE) of 20.15%, with a short-circuit current density (JSC) of 22.60 mA/cm2 and open-circuit voltage (VOC) of 1.14 V. This outcome indicates that PTAA:NPB composite materials present great potential for fabricating high-performance PSCs.
关键词： Energy level alignment,Charge extraction,π-conjugated molecule
更新于2025-09-11 14:15:04
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Comparative study of photoluminescence for type-I InAs/GaAs0.89Sb0.11 and type-II InAs/GaAs0.85Sb0.15 quantum dots
摘要： InAs quantum dots (QDs) sandwiched inside a GaAsSb matrix possess advantages for achieving telecom wavelength lasers and for developing high efficiency solar cells. In this work, optical properties of InAs quantum dots (QDs) capped by GaAs1-xSbx (x ? 0.11 and 0.15) are comparatively investigated. The photoluminescence measurements reflect that the energy state filling, thermal activation, quenching, and lifetime of the carriers in InAs/GaAs0.89Sb0.11 QDs are different from those in the InAs/GaAs0.85Sb0.15 QDs. These differences are attributed to the band alignment transition from type-I to type-II resulting from the Sb-composition change from x ? 0.11 to x ? 0.15 in the GaAs1-xSbx capping layer. Therefore, the emission and quenching involve excited states for type-I InAs/GaAs0.85Sb0.15 QDs, but involve InAs QDs as well as the GaAs0.85Sb0.15 QW recombination for type-II InAs/GaAs0.85Sb0.15 QDs. So the luminescence reveals complex and distinct physics mechanisms for these two samples.
关键词： Photoluminescence,Quantum dots,Band alignment,Semiconductor compound
更新于2025-09-11 14:15:04
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Symmetry of molecular Rydberg states revealed by XUV transient absorption spectroscopy
摘要： Transient absorption spectroscopy is utilized extensively for measurements of bound- and quasibound-state dynamics of atoms and molecules. The extension of this technique into the extreme ultraviolet (XUV) region with attosecond pulses has the potential to attain unprecedented time resolution. Here we apply this technique to aligned-in-space molecules. The XUV pulses are much shorter than the time during which the molecules remain aligned, typically <100 fs. However, transient absorption is not an instantaneous probe, because long-lived coherences re-emit for picoseconds to nanoseconds. Due to dephasing of the rotational wavepacket, it is not clear if these coherences will be evident in the absorption spectrum, and whether the properties of the initial excitations will be preserved. We studied Rydberg states of N2 and O2 from 12 to 23 eV. We were able to determine the polarization direction of the electronic transitions, and hence identify the symmetry of the final states.
关键词： transient absorption spectroscopy,extreme ultraviolet,attosecond pulses,molecular alignment,Rydberg states
更新于2025-09-11 14:15:04
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Direct Observation of Conductive Polymer Induced Inversion Layer in n‐Si and Correlation to Solar Cell Performance
摘要： Heterojunctions formed by ultrathin conductive polymer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)—PEDOT:PSS] films and n-type crystalline silicon are investigated by photoelectron spectroscopy. Large shifts of Si 2p core levels upon PEDOT:PSS deposition provide evidence that a dopant-free p–n junction, i.e., an inversion layer, is formed within Si. Among the investigated PEDOT:PSS formulations, the largest induced band bending within Si (0.71 eV) is found for PH1000 (high PEDOT content) combined with a wetting agent and the solvent additive dimethyl sulfoxide (DMSO). Without DMSO, the induced band bending is reduced, as is also the case with a PEDOT:PSS formulation with higher PSS content. The interfacial energy level alignment correlates well with the characteristics of PEDOT:PSS/n-Si solar cells, where high polymer conductivity and sufficient Si-passivation are also required to achieve high power conversion efficiency.
关键词： core level shifts,band bending,PEDOT:PSS/Si solar cell,energy level alignment,inversion layer
更新于2025-09-11 14:15:04
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A simple jig for the anti-parallel alignment of linacs’ lasers
摘要： Background: Despite crossing at the isocentre, misaligned laser beams may cause significant positioning problems. Purpose: The jig proposed here is to be used in addition to the quality assurance procedures employed with linacs and deals with possible misalignments of transverse lasers. Materials and methods: It is an inverted T construction with a two-sided rectangular, slightly transparent mirror set vertical on a piece of glass serving as its base. The device is carried by a horizontally set spirit-level surface and placed on the couch-top so that the sagittal laser passes through the vertical mirror’s plane. Then the therapy couch is translated along the Y direction until a laser beam shines on the corresponding side of the semi-transparent mirror. This spot is marked and is normally the linac’s isocentre set through an independent procedure employing a rotating plate. If the laser had been set properly, then its beam should be reflecting back on its source. If not, the alignment can be corrected by rotating and/or translating the laser holder until it does that. At the same time, it should be ensured that the beam does not wander away from the isocentre spot on the mirror. When both are achieved, the beam ends up perpendicular to the linac’s axis of rotation, while passing through the isocentre. The procedure can be repeated for the opposite laser. Conclusion: The jig was simple to construct and has been found quite useful in practice. The accuracy of patient positioning will be restricted only by the size of the laser beam’s cross-section.
关键词： laser alignment,patient positioning,radiotherapy,laser beam set up
更新于2025-09-11 14:15:04
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Minimizing Voltage Loss in Efficient All-inorganic CsPbI2Br Perovskite Solar Cells through Energy Level Alignment
摘要： All-inorganic CsPbI2Br, prized for its strong stability against thermal aging and light soaking, has attracted intensive attention. However, a large energy loss results from the serious energy level offset of 1.05 eV between CsPbI2Br and Spiro-MeOTAD, hindering further efficiency improvement of PSCs. To address this issue, a moderate energy level (CsPbI2Br)1-x(CsPbI3)x layer has been introduced at the interface between CsPbI2Br and Spiro-MeOTAD to form graded energy level alignment. The interpolation of which has offered the energy level gradient for reducing the resistance of hole transport. Correspondingly, the energy level tailoring has minimized the energy loss and a remarkable VOC improved from 1.12 V to 1.32 V, which is one of the highest values for CsPbI2Br based solar cells. A relatively good thermal stability has also been validated. These good performances indicate that setting an intermediate energy level alignment will be a potential strategy for idealized device architecture to minimize energy loss.
关键词： Thermal Stability,Voltage Loss,Energy Level Alignment,All-inorganic CsPbI2Br,Perovskite Solar Cells
更新于2025-09-11 14:15:04
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Studies of the liquid crystal surface anchoring potential using Grandjean–Cano wedge
摘要： We extend further the theoretical and experimental studies of the actual surface anchoring potential restoration by polarisation microscope technique and using micro-images in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean–Cano (GC) Wedge). To realize the theoretically predicted options of observation of large director deviation angles from the easy axes, the experimental studies of director distribution in GC zones were performed for differing easy axes orientations at the wedge surfaces in white light. A weak surface anchoring at one wedge surface was obtained by a photo-alignment technique. A strong surface anchoring at the second wedge surface was obtained by a rubbing. There were observed for the first time jump-less walls (without jumps of the director orientation) between neighbouring GC zones and jumps in colour in the Newton’s rings (lines) at the positions of the walls between GC zones. Qualitative explanations of the both phenomena are presented and an expression for the jump in colour value in the Newton’s rings (lines) at the positions of the walls between GC zones is presented. Some experimentally found by the polarisation microscope and by the microphoto technique images demonstrate jump-less walls between the first GC zones. To ensure optimal parameters of the further experiments on the actual surface anchoring potential restoration, theoretical calculations of the director distribution in individual GC zones were performed for various model surface anchoring potentials. It was found that especially promising for description of the experimentally found director distribution looks the modified D-potential. As a result of the present studies, the ways to enlarge (compared to the previous studies) angular range of the actual surface anchoring potential restora- tion were proposed.
关键词： photo alignment,polarisation microscope technique,surface anchoring potential restoration,Grandjean–Cano wedge
更新于2025-09-11 14:12:44
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Automatic Image Alignment Using Principal Component Analysis
摘要： We present an automatic technique for image alignment using principal component analysis (PCA) that broadly consists of two steps. The first step is the segmentation of the region of interest by thresholding. In the second step, PCA is applied on nonzero pixels in the binary image to determine the object rotation about the mean of the object pixels. Existing PCA-based techniques align the data in their principal spread; however, they have a critical problem of 180? rotation in their principal axes. The current paper provides an automatic solution to address this problem. The algorithm is based on assignment rules inferred from the eigenvectors given by PCA. We applied the proposed algorithm to different datasets including handwritten images of digits, a rotated fingerprint image dataset, and a dataset of magnetic resonance brain images, and confirmed that the proposed method aligns the data efficiently and accurately. In addition to alignment, the algorithm proposes two standard orientations for automatically assessing the true side (upside) of an object.
关键词： fingerprint alignment,digit alignment,Image alignment,PCA,image registration
更新于2025-09-10 09:29:36
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Image-Alignment Based Matching for Irregular Contour Defects Detection
摘要： Automatic defect inspection is attractive for high-quality workpiece manufacturing with irregular contours in order to achieve high accuracy and no contour defect. Thus, a novel image alignment-based feature matching algorithm framework is proposed in this paper. It can be used to solve the specified pixel-level defect detection and location problems for workpieces with irregular contours. A new forensic hash is firstly generated by extracting the scale, position and main orientation information of feature points. Since the forensic hash is invariant to rotation, translation and scaling, it is used for feature matching. A feature matching method based on a robust cascade estimator is secondly proposed to establish an accurate correspondence between the test image and reference image according to the obtained image hash and a parameter space voting mechanism. Thirdly, the matched feature points are used to estimate the similar transformation parameters to achieve an accurate image alignment. Finally, image difference and morphological technique are used to locate the contour defect. Experimental results demonstrate that the proposed algorithm can effectively detect and locate small contour defects in irregular stamping workpieces.
关键词： Feature matching,Irregular contour,Visual inspection,Image alignment
更新于2025-09-10 09:29:36
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Centroid and Covariance Alignment-Based Domain Adaptation for Unsupervised Classification of Remote Sensing Images
摘要： A new domain adaptation algorithm based on the class centroid and covariance alignment (CCCA) is proposed for classification of remote sensing images. This approach exploits both the first- and second-order statistics to describe the data distribution and aligns the data distribution between domains on a per-class basis. Since the predicted labels of target data are used to estimate the two statistics, we applied overall centroid alignment (OCA) as a coarse domain adaptation strategy to improve the estimation accuracy. In addition, the OCA coarse adaptation in conjunction with CCCA refined adaptation can also benefit by incorporation of spatial information, resulting in a Spa_OCA_CCCA approach. The proposed approach is easy to implement, and only one parameter is required in the spatial filtering step. It does not require labeled information in the target domain and can achieve labor-free classification. The experimental results using Hyperion, National Center for Airborne Laser Mapping, and Worldview-2 remote sensing images demonstrated the effectiveness of the proposed approach.
关键词： Alignment,remote sensing,domain adaptation,classification
更新于2025-09-10 09:29:36