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A CNN With Multiscale Convolution and Diversified Metric for Hyperspectral Image Classification
摘要： Recently, researchers have shown the powerful ability of deep methods with multilayers to extract high-level features and to obtain better performance for hyperspectral image classification. However, a common problem of traditional deep models is that the learned deep models might be suboptimal because of the limited number of training samples, especially for the image with large intraclass variance and low interclass variance. In this paper, novel convolutional neural networks (CNNs) with multiscale convolution (MS-CNNs) are proposed to address this problem by extracting deep multiscale features from the hyperspectral image. Moreover, deep metrics usually accompany with MS-CNNs to improve the representational ability for the hyperspectral image. However, the usual metric learning would make the metric parameters in the learned model tend to behave similarly. This similarity leads to obvious model’s redundancy and, thus, shows negative effects on the description ability of the deep metrics. Traditionally, determinantal point process (DPP) priors, which encourage the learned factors to repulse from one another, can be imposed over these factors to diversify them. Taking advantage of both the MS-CNNs and DPP-based diversity-promoting deep metrics, this paper develops a CNN with multiscale convolution and diversified metric to obtain discriminative features for hyperspectral image classification. Experiments are conducted over four real-world hyperspectral image data sets to show the effectiveness and applicability of the proposed method. Experimental results show that our method is better than original deep models and can produce comparable or even better classification performance in different hyperspectral image data sets with respect to spectral and spectral–spatial features.
关键词： deep metric learning,determinantal point process (DPP),image classification,multiscale features,Convolutional neural network (CNN),hyperspectral image
更新于2025-09-23 15:23:52
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Theoretical study of the effects of modifying the structures of organic dyes based on N,N-alkylamine on their efficiencies as DSSC sensitizers
摘要： In this work, we carried out a theoretical study in which DFT and TD-DFT calculations of a series of six new organic dyes that incorporate N,N-alkylamine as an electron donor and a cyanoacrylic acid group as an electron acceptor and anchoring group were performed. In each dye, the donor and the acceptor were bridged by six different π-conjugated spacers consisting of an auxiliary donor group (3,4-ethylenedioxythiophene, EDOT) or an auxiliary acceptor group (benzothiadiazole, BTZ or diketopyrrolopyrrole, DPP) that was linked to either thiophene or phenyl. EHOMO, ELUMO, Egap, λmax, Eex, the open-circuit photovoltage (Voc), the light-harvesting efficiency (LHE), and the free injection energy (ΔGinject) were calculated for all of the dyes to compare their photovoltaic performance. The effects of the incorporation of an additional acceptor group (DPP or BTZ) or an additional donor group (EDOT) into the π-bridge on the geometry, electronic structure, and photovoltaic performance of each designed dye were explored. The study shows that modifying the dye skeleton can greatly improve the performance of the dye and increase its power conversion efficiency. It also reveals that all of the studied dyes are promising candidates for an effective DSSC sensitizer, especially those that include the acceptor group DPP in the π-bridge.
关键词： DSSC,BTZ,N,N-alkylamine,DPP,EDOT
更新于2025-09-23 15:22:29
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Theoretical study of new conjugated compounds with a low bandgap for bulk heterojunction solar cells: DFT and TD-DFT study
摘要： Bulk heterojunction solar cells have attracted scientific and economic interest in recent years, and have just been one of the future photovoltaic technologies to produce energy at low cost. To study the electronic and geometric properties of a novel conjugated polymer called r-PTTDPP50, which is formed from a derivative of diketopyrrolopyrrole (DPP), thiophene conjugated side chain and 2, 5-bis (trimethylstannyl) thiophene, functional density theory (DFT) has been used with several methods such as B3LYP, PBEPBE, B3PW91 and mPW1PW91 and the basis set 6-31G (d, p),to obtain the most appropriate method. The absorption properties have been obtained by the CAM-B3LYP method. Then, the functional tests giving the closest result to the experimental ones will be used to propose other structure candidates for applications in the domain of organic electronics. This research has been used to conduct next syntheses to compounds more helpful as active materials in optoelectronic.
关键词： Bulk heterojunction,DFT,solar cells,diketopyrrolopyrrole (DPP),thiophene
更新于2025-09-23 15:21:01
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Structural and Electronic Origin of Bis-Lactam Based High Performance Organic Thin Film Transistors
摘要： We describe herein the comprehensive theoretical and experimental studies on the transistor mobility of organic semiconductors by correlating two-dimensional (2D) intermolecular interaction with thin film morphology and the electronic coupling structure. We developed a novel bis-lactam based small molecule, 1,5-dioctyl-3,7-di(thiophen-2-yl)-1,5-naphthyridine-2,6-dione (C8-NTDT) with 2D-type C-H···O=C intermolecular interaction along the in-plane directions of crystal packing structure, which is characteristically different from the 1D-type intermolecular interaction shown in the typical bis-lactam molecule of C8-DPPT. Experimentally and theoretically, C8-NTDT exhibited more favorable thin film morphology and electronic coupling structure for charge transport due to their unique 2D intermolecular interactions compared with C8-DPPT. In fact, C8-NTDT exhibited hole mobility of up to 1.29 cm2 V-1 s-1 and on/off ratio of 107 in vacuum processed device. Moreover, the high solubility with 2D electronic coupling structure of C8-NTDT enables versatile solution processing for device fabrication without performance degradation compared to the vacuum processed device. As an example, we could demonstrate hole mobility of up to 1.10 cm2 V-1 s-1 for the spin-coated devices, which is one of the best performance among the solution processed organic field effect transistors based on bis-lactam containing small molecules.
关键词： Organic Field Effect Transistor,Bis-Lactam,NTD,DPP,2D
更新于2025-09-19 17:15:36
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Theoretical Studies of Photophysical Properties of Da????a??Aa????a??D-Type Diketopyrrolopyrrole-Based Molecules for Organic Light-Emitting Diodes and Organic Solar Cells
摘要： A series of D–π–A diketopyrrolopyrrole(DPP)-based small molecules were designed for organic light-emitting diode(OLEDs) and organic solar cell(OSCs) applications. Applying the PBE0/6-31G(d,p) method, the ground state geometry and relevant electronic properties were investigated. The first excited singlet state geometry and the absorption and fluorescent spectra were simulated at the TD-PBE0/6-31G(d,p) level. The calculated results revealed that the photophysical properties were affected through the introduction of different end groups. Furthermore, the electronic transitions corresponding to absorption and emission exhibited an intramolecular charge transfer feature. Our results suggest that the designed molecules acted not only as luminescent for OLEDs, but also as donor materials in OSCs. Moreover, they can also be used as potential electron transfer materials for OLEDs and OSCs.
关键词： photophysical properties,organic solar cells(OSCs),organic light-emitting diodes(OLEDs),diketopyrrolopyrrole(DPP)-based molecules,Charge transporting property
更新于2025-09-19 17:13:59
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Power rating analysis and protection for photovoltaic-isolated port based differential power processing systems
摘要： In a photovoltaic generation system (PGS), photovoltaic (PV) modules are often connected in series for increased string voltage. However, a significant reduction in the actual output power is observed due to the manufacturing tolerance, module aging and partial shaded. Compared with conventional methods such as bypass diodes and PV module reconfiguration, modular distributed architecture especially the differential power processing (DPP) is able to yield high output power even under partial shading conditions. Moreover, the system efficiency is improved since only the differential power is processed by the DPP converters. This paper mainly focuses on the power rating analysis and protection of PV-isolated Port (PV-IP) based DPP systems considering the significant power stress difference among DPP converters under different partial shading conditions. The voltage equalization (VE) control used in this work is able to provide up to 77% efficiency improvement through the simulation evaluation. The protection algorithm is proposed for the PV-IP DPP architecture to improve the system reliability even when some DPP converters are found failed. With the proposed protection strategy, not only the high output power yield can be maintained, but also the modular design of DPP converters with smaller power capacity can be achieved. Simulation and indoor experimental tests under various partial shading conditions were carried out to validate the effectiveness of the proposed power rating analysis and protection scheme.
关键词： Partial shading,Differential power processing (DPP),Power rating,PV submodule integrated converter (subMIC),Optimization,PV-Isolated Port (PV-IP) DPP
更新于2025-09-16 10:30:52
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Power recovery and equalization in partially shaded photovoltaic strings by an efficient switched capacitor converter
摘要： Partial shading is the major complication encountered by the Photovoltaic strings while delivering maximum power to the load. This scenario consequently diminishes the functionality of the modules causing mismatch, hotspot, power loss and multiple peaks formation in the characteristics curves of the strings. Also, formation of multiple peaks affects the performance of the maximum power point trackers due to false tracking resulting in severe power loss. In this paper, a switched-capacitor converter for power recovery and equalization in the strings during shading is proposed. The parallel-ladder architecture of the converter maintains voltage ratios by transferring power between the shaded and unshaded modules of the strings. The converter enables the string to generate maximum power by ensuring single peak in the characteristics curves during shading. The performance of the string with the proposed converter is compared to conventional strings using characteristics curves, and various performance parameters. The systems are tested in MATLAB/Simulink and experimental setup under various static and dynamic partial shading conditions. Also, the conduction losses encountered by the converter during power balancing in the strings are analysed and expressed mathematically. The results clearly indicate that the proposed converter can be easily implemented in the strings to recover the power losses and avoid multiple peaks formation in the characteristics curves during partial shading with efficiency greater than 99%.
关键词： Maximum power point,Photovoltaic (PV) strings,Partial shading,Differential power processing (DPP),Switched-capacitor (SC) converter
更新于2025-09-16 10:30:52
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Fluorinated dithienyl-diketopyrrolopyrrole: a new building block for organic optoelectronic materials
摘要： Diketopyrrolopyrrole (DPP) derivatives have been widely used as the electron-withdrawing unit to construct donor–acceptor (D–A) conjugated systems in organic electronics. The 3,6-position flanking aromatic rings of DPP could strongly influence the optoelectronic properties of DPP-based materials. In this study, a stepwise synthesis strategy was used to prepare monofluorinated and difluorinated dithienyl-DPP. The single crystal of the difluorinated model compound was also obtained. Three polymers based on bithiophene donor and dithienyl-DPP acceptor with different fluorinated positions were synthesized. And preliminary investigations of the influence of fluorination on the optoelectronic properties were performed.
关键词： dithienyl-DPP,Diketopyrrolopyrrole,optoelectronic properties,organic electronics,fluorinated
更新于2025-09-16 10:30:52
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Broadband polymer photodetectors with a good trade-off between broad response and high detectivity by using combined electron-deficient moieties
摘要： High-performance broadband photodetectors based on low-bandgap conjugated polymers are scarce due to a trade-off between the photoresponse range and device performance. In this work, the polymers with structural features responsible for both broad response and high detectivity are realized by using the combined electron deficient moieties at the molecular level. Based on the electron-deficient diketopyrrolopyrrole (DPP) and benzothiadiazole (BT), the combined units of DPP-DPP and DPP-BT-DPP are deemed more electron deficient and were successfully incorporated into the corresponding polymers. The arrangement of electron deficient moieties in the polymer mainchain were found to be able to greatly affect the absorption profile, energy level, molecular stacking, and blend film morphology. Consequently, the photodetector based on the polymer with DPP-BT-DPP acceptor exhibited the D* value of over 1012 Jones in the spectral region of 320–930 nm under -0.1 V bias.
关键词： low-bandgap conjugated polymers,electron deficient moieties,high detectivity,DPP,broadband photodetectors,BT
更新于2025-09-16 10:30:52
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Computational study on optoelectronic and charge transport properties of diketopyrrolopyrrole-based A–D–A–D–A structure molecules for organic solar cells
摘要： Eight novel diketopyrrolopyrrole (DPP)-based A–D–A–D–A structure molecules were designed for organic solar cells (OSCs) applications. In these molecules, the electron-deficient DPP and dicyanovinyl groups were used as the acceptor groups and different planar electron-rich groups were employed as the donor π-bridges. Applying the B3LYP/6–31G (d,p) and TD-B3LYP/6–31G (d,p) methods, the optoelectronic and charge transport properties were investigated. It turned out that the different π-bridges can tune effectively the frontier molecular orbital energy levels, band gap, and absorption spectra. Furthermore, the different π-bridges also affect the charge transport properties of the designed molecules. Our results suggest that the investigated molecules can serve as donor materials. Additionally, some investigated molecules can also be used as hole and/or electron transport materials for OSCs.
关键词： Optoelectronic property,Dicyanovinyl,Reorganization energy,Diketopyrrolopyrrole (DPP),Organic solar cells (OSCs)
更新于2025-09-12 10:27:22