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Facile-effective Hole Transporting Materials Based on Dibenzo[a,c]carbazole: The Key Role of Linkage Position to Photovoltaic Performance of Perovskite Solar Cells
摘要： Film morphology of hole-transporting layer is proved as the key element to charge transfer and interfacial property in perovskite solar cells. In this text, a new dibenzo[a,c]carbazole (DBC) core with multiple reaction sites has been formed with Y-shape, in which, the phenathrene group was integrated as a plane π structure into the common carbazole moiety. Accordingly, three DBC-based hole-transporting materials (HTMs) with varied molecular configurations were synthesized by the introduction of N-(4-methoxyphenyl)-9,9-dimethyl-9H-fluoren-2-amine (F(Me)NPh) as the periphery groups at different linkage positions. Once being applied to perovskite solar cells as HTMs, DBC-2 with the twisted and asymmetric structure achieved the highest conversion efficiency of 20.02%. Also, the corresponding dopant-free device exhibited the PCE of 16.43% and good device stability, under glovebox and ambient conditions.
关键词： hole-transporting materials,dibenzo[a,c]carbazole,perovskite solar cells,molecular configurations,photovoltaic performance
更新于2025-09-11 14:15:04
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Grid Connected-Photovoltaic System (GC-PVS): Issues and Challenges
摘要： Smart grid is the key technology for an effective utilization of the Renewable Energy Sources (RES). The utilization of RES for the generation of electricity is increasingly gaining interest of researchers during the last decades. The main reason behind this is global incentivization, the increasing price of petroleum products, climate issues and deregulations in the energy market. As the Government of India, (MNRE i.e. Ministry of New & Renewable Energy) is targeting to generate 20000 MW power through grid-connected solar PVS by the year 2022 therefore, the main focus in this paper has been presented on power generation through grid-connected PVS. The emerging smart grid technology has enabled the grid-connected PVS as an evolving process in today’s world for electrical power generation. However, apart from so many advantages, there are several issues and challenges associated with the integration of PVS to the electric utility grid hence, the investigation to find out available possible solutions to overcome these issues becomes essential in order to enhance the performance of grid-connected PVS. The most severe constraint associated with this emerging technology is it high penetration level. If during low load conditions there is some mismatch found between the real power output and the load profile characteristics of PVS then it may result into large reverse power flow, high power losses or severe voltage violation. In this paper, several issues and challenges associated with the integration of solar PVS with the electric utility grid are presented.
关键词： Renewable Energy Sources,Grid Connected-Photovoltaic System,harmonics,voltage stability,RES,frequency stability,smart grid,GC-PVS
更新于2025-09-11 14:15:04
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Self-assembled NiO microspheres for efficient inverted mesoscopic perovskite solar cells
摘要： Perovskite solar cells (PSCs) with both normal (n-i-p) and inverted (p-i-n) mesoscopic structures usually exhibit higher e?ciency than their planar counterparts because the mesoporous charge transport layers can supply heterogeneous nucleation sites for growing high quality perovskite crystals and enlarged charge separation area for better charge extraction. However, comparing with the achieved extremely high or even the certi?ed world record e?ciency of mesoscopic PSCs, the signi?cant improvement of inverted mesoscopic PSCs has yet been made, mainly owing to the lack of suitable p-type semiconductors for preparing mesoporous hole transport layers (HTLs). Here, an emulsion-based bottom-up self-assembly strategy is used to prepare NiO microspheres from well-dispersed NiO nanocrystals. The self-assembled NiO microspheres are further used to fabricate mesoporous NiO HTLs of the inverted mesoscopic PSCs. The as-prepared mesoporous NiO HTL with self-assembled NiO microspheres can provide more suitable graded energy alignment, better charge carrier dynamics and reduced dark recombination in the device comparing with the inverted planar PSC with NiO nanocrystal HTL, contributing to obviously enhanced photovoltaic performance and nearly eliminated photocurrent-voltage hysteresis. Due to the general strategy of emulsion-based bottom-up self-assembly for microspheres synthesis, it will overcome the shortage of p-type materials for preparing e?cient inverted mesoscopic PSCs.
关键词： Self-assembled NiO microspheres,Photovoltaic performance,Inverted mesoscopic perovskite solar cell
更新于2025-09-11 14:15:04
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Numerical Performance Evaluation of Solar Photovoltaic Water Pumping System under Partial Shading Condition using Modern Optimization
摘要： Renewable energy is an attractive solution for water pumping systems particularly in isolated regions where the utility grid is unavailable. An attempt is made to improve the performance of solar photovoltaic water pumping system (SPVWPS) under partial shading condition. Under this condition, the power versus voltage curve has more than one maximum power point (MPP), which makes the tracking of global MPP not an easy task. Two MPP tracking (MPPT) strategies are proposed and compared for tracking MPP of SPVWPS under shading condition. The first method is based on the classical perturb and observe (P&O) and the other method is based on a Salp Swarm Algorithm (SSA). Based on extensive MATLAB simulation, it is found that the SSA method can provide higher photovoltaic (PV) generated power than the P&O method under shading condition. Consequently, the pump flowrate is increased. But, under normal distribution of solar radiation, both MPPT techniques can extract the maximum power but SSA is considered a time-consuming approach. Moreover, SSA is compared with particle swarm optimization (PSO) and genetic algorithm (GA). The obtained results ensure the superiority of SSA compared with PSO and GA. SSA has high successful rate of reaching true global MPP.
关键词： water pumping,solar photovoltaic,numerical evaluation,modern optimization
更新于2025-09-11 14:15:04
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[IEEE 2018 International Conference on Circuits and Systems in Digital Enterprise Technology (ICCSDET) - Kottayam, India (2018.12.21-2018.12.22)] 2018 International Conference on Circuits and Systems in Digital Enterprise Technology (ICCSDET) - Performance Analysis of Solar Photovoltaic System with Fuzzy Based Variable Step Size MPPT Algorithm Using Matlab /Simulink
摘要： In the recent decades, Photovoltaic (PV) power generation has become one of the primary power source due to the advantages such as less maintenance and environmental benefits. Moreover, the generation source is ultimately free and abundant. However, the major barriers related to PV power generation are low power conversion efficiency, high cost of PV modules and nonlinearity in output power. Because of low power conversion efficiency, PV systems should work always at its Maximum Power Point (MPP). A power conditioning unit with Maximum Power Point Tracking (MPPT) technique is employed in the PV systems to harvest maximum power. The main function of MPPT is to detect the MPP for the given conditions and operate the system at that point. In this paper Fuzzy Logic Controller (FLC) based variable step size MPPT for a standalone solar PV system is presented. Solar PV system with Fuzzy based MPPT controller in Matlab /Simulink. The performance of proposed variable step size fuzzy MPPT algorithm is studied for different input conditions and analyzed in terms of performance parameters such as tracking speed, steady state oscillations, response under variations in irradiance and temparature, average output power and output power ripple. The results are compared with Variable Step Size Incremental Conductance (VSS InC) MPPT algorithm and conventional InC based PV system.
关键词： Solar Photovoltaic (SPV),Fuzzy Logic Control (FLC),MATLAB/Simulink,Simulation,Variable Step Size Incremental Conductance (VSS InC),Maximum Power Point Tracking (MPPT)
更新于2025-09-11 14:15:04
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[IEEE 2019 8th International Conference on Modern Power Systems (MPS) - Cluj Napoca, Romania (2019.5.21-2019.5.23)] 2019 8th International Conference on Modern Power Systems (MPS) - Assessment of Photovoltaic Modules' Parameters Using the On-Site Measurements
摘要： Among various renewable energy sources, the photovoltaic technology is considered the proper technology for distributed power generation. The performance of electrical photovoltaic depends on their characteristics on various environmental conditions. The objective of this paper is to use the one-diode model together with on-site measurements, in order to evaluate the current-voltage and power-voltage curves and effects of irradiance and temperature on the performance the photovoltaic panel.
关键词： one-diode model,simulation,photovoltaic panel,data acquisition
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Revealing phase separation and crystallinity in small molecule solar cells using 3D electron microscopy
摘要： Transmission Electron Microscopy (TEM) can be utilized to understand the morphology of organic bulk heterojunction (BHJ) solar cells and thus aid in improving device performance. We have previously shown that phase separation and formation of crystallinity is to be expected during co-evaporation of small molecule BHJ layers [1]. Using Electron Spectroscopic Imaging (ESI) [2] and electron diffraction, we found a significant influence of substrate and substrate temperature on the morphology of the photoactive layer during the fabrication of F4ZnPc:C60 BHJs. Whether or not the device is fabricated as inverted [3] or non-inverted cell influences crystal growth and, thus, phase separation during film formation. We have found that heating the substrate during BHJ film formation leads to an increase in efficiency for the inverted cell, whereas the non-inverted device shows no improvement. While the ESI measurements showed that substrate heating facilitates phase separation of the two materials, the difference in efficiency of the different device architectures could not be explained by this. Electron diffraction data indicated that crystallinity plays a role here. Since conventional ESI and electron diffraction only provide information about material distribution and crystallinity in a two-dimensional projection of the BHJ layers, high-resolution electron tomography was performed to gain insight into the three-dimensional structure. F4ZnPc:C60 was co-evaporated onto layers of neat F4ZnPc and C60, respectively. The measurements were performed under low-dose and LN2-cryo conditions in an FEI Titan Krios. This was necessary to preserve the sample, and foremost its crystallinity, since carbon-based materials, like C60, are prone to severe damage by electron irradiation. Figure 1 shows a bright-field TEM image of the BHJ on C60 (gold fiducials, seen in black, were used for tilt-series alignment). All images of the acquired tilt-series show crystalline areas such as the ones marked (A,B,C). The crystalline spacing seen here can be identified in the power spectra as characteristic for C60 (red: 0.85 nm, green: 0.5 nm and blue: 0.44 nm). As illustrated, such crystallinity can also be visualized in high-resolution electron tomograms, albeit only for smaller volumes at quite high magnification. To obtain a statistically significant distribution of crystallinity for different cell architecture and cell fabrication, larger volumes need to be analysed. For a given detector size, one needs to apply lower magnifications which results in lower resolution. However, the signature of pure crystals at these imaging conditions are a low variance in 3D, i.e. crystal distributions can easily be obtained from segmented 3D variance maps. A slice through the tomographic reconstruction of such samples can be seen in figure 2. Here, a BHJ film on C60 substrate is compared with a similar section through a tomogram of the BHJ on F4ZnPc. The gold fiducial indicates the top of the BHJ film. The homogeneous, aka crystalline areas are highlighted (red overlay). From the distribution of crystallinity we deduce, that large C60 crystals are found in both device architectures causing a very rough film surface. In the inverted device, these crystals can extend throughout the whole film, using the polycrystalline C60 substrate as seed for crystal growth, whereas the non-inverted BHJ showed C60 crystals starting somewhere in the middle of the film. Correlating this data with device performance, we find that C60 crystals which have grown throughout the BHJ layer are crucial for efficient devices.
关键词： Solar Cells,Crystallinity,Tomography,Organic Photovoltaic,CryoTEM
更新于2025-09-11 14:15:04
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Stress and Fracture of Crystalline Silicon Cells in Solar Photovoltaic Modules – A Synchrotron X-ray Microdiffraction based Investigation
摘要： Fracture of crystalline silicon (c-Si) solar cells in photovoltaic modules is a big concern to the photovoltaics (PV) industry. Cell cracks cause performance degradation and warranty issues to the manufacturers. The roots of cell fractures lie in the manufacturing and integration process of the cells and modules as they go through a series of elevated temperature and pressure processes, involving bonding of dissimilar materials, causing residual stresses. Evaluation of the exact physical mechanisms leading to these thermomechanical stresses is highly essential to quantify them and optimize the PV modules to address them. We present a novel synchrotron X-ray microdiffraction based techniques to characterize the stress and fracture in the crystalline silicon PV modules. We show the detailed stress state after soldering and lamination process, using the synchrotron X-ray microdiffraction experiments. We also calculate the maximum tolerable microcrack size in the c-Si cells to sustain the residual stress after lamination. We further demonstrate the effect of these residual stresses on the cell fractures using the widely accepted fracture (4-point bending) tests. These test results show that the soldering and lamination induced localized residual stresses indeed reduce the load-carrying capacity of the c-Si cells.
关键词： fracture,crystalline silicon,residual stresses,synchrotron X-ray microdiffraction,photovoltaic modules
更新于2025-09-11 14:15:04
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Photocurrent Direction Control and Increased Photovoltaic Effects in All-2D Ultrathin Vertical Heterostructures Using Asymmetric h-BN Tunneling Barriers
摘要： Two-dimensional (2D) materials are atomically thick and without out-of-plane dangling bonds. As a result, they could break the con?nement of lattice matching, and thus can be freely mixed and matched together to construct vertical van der Waals heterostructures. Here, we demonstrated an asymmetrical vertical structure of graphene/hexagonal boron nitride (h-BN)/tungsten disul?de (WS2)/graphene using all chemical vapor deposition grown 2D materials. Three building blocks are utilized in this construction: conductive graphene as a good alternative for the metal electrode due to its tunable Fermi level and ultrathin nature, semiconducting transition-metal dichalcogenides (TMDs) as an ultrathin photoactive material, and insulating h-BNas a tunneling barrier. Such an asymmetrical vertical structure exhibits a much stronger photovoltaic e?ect than the symmetrical vertical one without h-BN. By changing the sequence of h-BN in the vertical stack, we could even control the electron ?ow direction. Also, improvement has been further made by increasing the thickness of h-BN. The photovoltaic e?ect is attributed to di?erent possibilities of excited electrons on TMDs to migrate to top and bottom graphene electrodes, which is caused by potential di?erences introduced by an insulating h-BN layer. This study shows that h-BN could be e?ectively used as a tunneling barrier in the asymmetrical vertical heterostructure to improve photovoltaic e?ect and control the electron ?ow direction, which is crucial for the design of other 2D vertical heterostructures to meet various needs of electronic and optoelectronic devices.
关键词： WS2,asymmetrical vertical heterostructure,photovoltaic,CVD,graphene,2D materials,h-BN
更新于2025-09-11 14:15:04
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Parameters Extraction of Photovoltaic Models Using an Improved Moth-Flame Optimization
摘要： Photovoltaic (PV) models’ parameter extraction with the tested current-voltage values is vital for the optimization, control, and evaluation of the PV systems. To reliably and accurately extract their parameters, this paper presents one improved moths-flames optimization (IMFO) method. In the IMFO, a double flames generation (DFG) strategy is proposed to generate two different types of target flames for guiding the flying of moths. Furthermore, two different update strategies are developed for updating the positions of moths. To greatly balance the exploitation and exploration, we adopt a probability to rationally select one of the two update strategies for each moth at each iteration. The proposed IMFO is used to distinguish the parameter of three test PV models including single diode model (SDM), double diode model (DDM), and PV module model (PMM). The results indicate that, compared with other well-established methods, the proposed IMFO can obtain an extremely promising performance.
关键词： moth-flame optimization,photovoltaic model,parameter extraction,double flames generation (DFG) strategy
更新于2025-09-11 14:15:04