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[IEEE 2019 54th International Universities Power Engineering Conference (UPEC) - Bucharest, Romania (2019.9.3-2019.9.6)] 2019 54th International Universities Power Engineering Conference (UPEC) - Harmonic Behaviour of RGB WLED
摘要： For the last few years, there has been a decrease in electricity consumption for lighting purposes. The reason for this decrease is the widespread use of energy saving lighting elements that have high efficacy factor. LEDs are one of these lighting elements and have a very important role on energy saving lighting. On the other hand, power quality problems have started to be experienced more frequently and seriously, so it has become an important issue nowadays. Light emitting diodes are a closely related in both subjects. In this study, the harmonic behavior of RGB WLEDs, which has gained importance recently and has become increasingly widespread, has been investigated. RGB WLEDs, which are quite different from monochrome LEDs in terms of package contents and driver circuit, are expected to behave differently in terms of harmonics. In order to observe that, an appropriate test setup has been established and the power quality measurements of an RBG WLED sample have been performed for different operating cases. In the conclusion of the study, the enlightening results about the harmonic behavior of RGB WLEDs were obtained.
关键词： RGB WLED,Light emitting diodes,Distortion measurement,Relative spectral power,Power conversion harmonics
更新于2025-09-11 14:15:04
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Co-Design of the PV Array and DC/AC Inverter for Maximizing the Energy Production in Grid-Connected Applications
摘要： Grid-connected Photovoltaic (PV) systems are currently developed by merging a PV array and a DC/AC inverter which are designed separately, without considering the impact of the PV array operational characteristics on the power losses of the DC/AC inverter. In this paper, a co-design technique is presented, where the optimal design parameters of the PV array and DC/AC inverter in a grid-connected PV system are calculated concurrently through a unified design process. The proposed technique enables to optimally match the PV array configuration and the DC/AC inverter structure. A study has been performed, where the PV systems synthesized by applying the proposed co-design technique are compared with PV system configurations comprising PV arrays and DC/AC inverters that have been designed separately, through distinct optimization processes based on various alternative optimization objectives. The design results for two installation sites, with different meteorological conditions during a year, demonstrated that only the proposed co-design optimization technique is capable to ensure the maximization of the annual energy production of the overall grid-connected PV system.
关键词： DC-AC power conversion,Optimization methods,Particle Swarm Optimization (PSO),Renewable Energy Sources (RES),Photovoltaic (PV) power systems
更新于2025-09-11 14:15:04
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Nonacyclic carbazole-based non-fullerene acceptors enables over 12% efficiency with enhanced stability for organic solar cells
摘要： In this work, a nonacyclic carbazole-cored electron-rich central building block called CZTT and its derivated non-fullerene acceptors (CZTT-IC and CZTT-4F) are designed and synthesized. CZTT-4F with fluorination on the accepting end groups shows significantly down-shifted energy levels and a narrower bandgap as well as a smaller dipole moment under the ground state in comparison to the counterpart CZTT-IC. In the blend films, blends of both fluorinated donor and acceptor (PM6:CZTT-4F) reveal relatively decreased miscibility resulting in better donor/acceptor interpenetrating network with higher domain purity for efficient charge transport. Organic solar cells (OSCs) based on PM6:CZTT-4F blend exhibited a highest power conversion efficiency (PCE) of 12.07% with enhanced thermal and light soaking stability. To the best of our knowledge, this performance is among the highest for carbazole-based OSCs in the literature. The results reveal that the nonacyclic CZTT core is a promising building block for constructing efficient non-fullerene acceptors. More importantly, the relatively decreased miscibility within fluorinated CZTT-based blend film is demonstrated to greatly promote the stability of OSCs.
关键词： stability,nonacyclic carbazole,non-fullerene acceptors,organic solar cells,power conversion efficiency
更新于2025-09-11 14:15:04
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Beneficial effects of potassium iodide incorporation on grain boundaries and interfaces of perovskite solar cells
摘要： Grain boundaries and interfacial impurities are the main factors that limit the further development of polycrystalline perovskite solar cells because their existence severely deteriorates the device performance. In order to optimize the efficiency of perovskite solar cells, it is essential to eliminate these defects. In the present work, potassium iodide (KI) is incorporated into the perovskite absorber. KI incorporation improves the crystallinity of the perovskite, increases the grain size, and decreases the contact potential distribution at the grain boundary, which are verified by X-ray diffraction, scanning electronic microscopy and Kelvin probe force microscopy. Besides, the activation energy of the recombination, estimated from the temperature dependent current–voltage of perovskite solar cells, is larger than the bandgap calculated from the temperature coefficient. These suggest that KI incorporation effectively passivates the grain boundaries and interfacial defects. As a result, charge trapping in the absorber as well as the bimolecular and trap-assisted recombination of the device are significantly suppressed. Consequently, the open circuit voltage and fill factor of the incorporated devices are greatly improved, enabling an optimized power conversion efficiency of 19.5%, in comparison with that of 17.3% for the control one. Our work provides an effective strategy of defect passivation in perovskite solar cells by KI incorporation and clarifies the mechanism of the performance optimization of KI incorporated devices.
关键词： potassium iodide,perovskite solar cells,defect passivation,grain boundaries,power conversion efficiency
更新于2025-09-11 14:15:04
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Graphene Quantum Dots Band Structure Tuned by Size for Efficient Organic Solar Cells
摘要： The electronic states of graphene quantum dots (GQDs) can be tuned by varying the lateral size and edge structure, which further influence their optoelectronic properties and the applications. In the work, three kinds of GQDs with different lateral size were prepared by photon-Fenton reaction and separated through gel column chromatography, and their effects on the photovoltaic performances of inverted organic solar cells based on the poly(3-hexylthiophene) (P3HT) and poly(3-hexylthiophene)/(6,6)-phenyl-C61 butyric acid methylester (PCBM) blend films were studied systematically. In comparing with P3HT:PCBM cells, the power conversion efficiency of the P3HT:PCBM solar cells containing 0.8% of GQDs-blue, GQDs-green, and GQDs-orange can be increased from 3.06 to 3.54, 4.43, and 3.73 % with a short-circuit current density of 10.3, 13.34, and 11.19 mA cm-2. It is illustrated also that the band structures (electronic energy states) tuned mainly by their lateral size of GQDs are the crucial factor to dominate their photovoltaic preferences as additives in conventional P3HT:PCBM solar cells.
关键词： power conversion efficiency,band structure,organic solar cells,graphene quantum dots
更新于2025-09-11 14:15:04
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Amorphous Polymer Acceptor Containing B ← N Units Matches Various Polymer Donors for All-Polymer Solar Cells
摘要： Polymer acceptors for high-efficiency all-polymer solar cells (all-PSCs) are generally semicrystalline. In this manuscript, we report an amorphous polymer acceptor, which matches well with a variety of polymer donors to produce efficient all-PSCs. The amorphous polymer acceptor (rr-PBN) is a regiorandom polymer consisting of alternating asymmetric B←N bridged thienylthiazole (BNTT) unit and pyridine-flanked diketopyrrolopyrrole (PyDPP) unit. It is amorphous in thin film because of its regiorandom structure and the large steric hindrance. rr-PBN shows deep LUMO/HOMO energy levels of ?3.71/?5.81 eV, strong sunlight harvesting capability and high electron mobility of 2.20 × 10?4 cm2 V?1 s?1. As a polymer acceptor, rr-PBN matches well with three commercially available polymer donors, J71, PTB7-Th, and PffBT4T-2OD to give excellent percolating bicontinuous network morphology in all-PSCs. We propose that the crystallization of polymer donors governs the film-forming process and dominates the phase separation morphology, leading to good phase separation morphology. The all-PSC devices all show power conversion efficiencies (PCEs) of 5.2?6.6%. This study provides a new direction to design polymer acceptors and a novel approach to control phase separation morphology of all-PSCs.
关键词： all-polymer solar cells,phase separation morphology,B←N units,amorphous polymer acceptor,power conversion efficiencies
更新于2025-09-11 14:15:04
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Green and simple preparation of carbon-coated iron pyrite thin films for solar cells application
摘要： Carbon-coated iron pyrite (FeS2@C) was prepared by a green and simple method. The utilization of an amorphous carbon-shell layer formed from a glucose source coated on the surface of core-pyrite nanoparticles. The FeS2@C thin film was formed by coating synthesized iron pyrite nanoparticles with a carbon layer and depositing the carbon-coated iron pyrite on a fluorine-doped tin oxide (FTO) substrate by spin-coating. The morphological, structural, and chemical composition properties of FeS2@C film was measured and characterized. Devices with the structure of FTO/TiO2/redox electrolyte/counter electrodes (FeS2@C, pristine FeS2, and Pt)/FTO were fabricated. The power conversion efficiency (PCE) of the FeS2@C-device (PCE ~ 6.94%), the pristine FeS2-device (PCE ~ 5.69%), the Pt-device (PCE ~ 6.48%). The improving of the device performance indicated that the FeS2@C thin film can be a good counter electrode (CE) for the performance of dye-sensitized solar cells (DSSCs).
关键词： Dye-sensitized solar cells,Carbon-coated iron pyrite,FeS2@C,Counter electrode,Power conversion efficiency
更新于2025-09-11 14:15:04
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Highly Selective and Scalable Fullerene-Cation-Mediated Synthesis accessing Cyclo[60]fullerenes with 5-Membered-Carbon-Ring and their Application to Perovskite Solar Cells
摘要： Cyclo[60]fullerenes are widely used in many applications including photovoltaic devices owing to their high electron affinity and mobility for an organic molecule. However, their synthesis has been limited to certain derivatives with low yields. In this work, a fullerene-cation-mediated synthesis, accessing a new class of 5-membered-carbon-ring cyclo[60]fullerenes with high yields of up to 93% is showcased. This method utilizes aryl[60]fullerene cations, ArC60+ as intermediates, which are generated in situ by heating the aryl[60]fullerenyl dimers in the presence of CuBr2. In addition, 5-membered-carbon-ring cyclo[60]fullerenes display excellent device applicability when they are used in perovskite solar cells as over-coating layers of electron-transporting layers. A power conversion efficiency of 20.7% is achieved thanks to the favorable energy alignment, optimized substrate design, and electrochemical stability of the 5-membered-carbon-ring fullerenes.
关键词： fullerene-cation-mediated synthesis,perovskite solar cells,5-membered-carbon-ring,cyclo[60]fullerenes,power conversion efficiency
更新于2025-09-11 14:15:04
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1 cm <sup>2</sup> Organic Photovoltaic Cells for Indoor Application with over 20% Efficiency
摘要： Organic photovoltaic (OPV) technologies have the advantages of fabricating larger-area and light-weight solar panels on flexible substrates by low-cost roll-to-toll production. Recently, OPV cells have achieved many significant advances with power conversion efficiency (PCE) increasing rapidly. However, large-scale solar farms using OPV modules still face great challenges, such as device stability. Herein, the applications of OPV cells in indoor light environments are studied. Via optimizing the active layers to have a good match with the indoor light source, 1 cm2 OPV cells are fabricated and a top PCE of 22% under 1000 lux light-emitting diode (2700 K) illumination is demonstrated. In this work, the light intensities are measured carefully. Incorporated with the external quantum efficiency and photon flux spectrum, the integral current densities of the cells are calculated to confirm the reliability of the photovoltaic measurement. In addition, the devices show much better stability under continuous indoor light illumination. The results suggest that designing wide-bandgap active materials to meet the requirements for the indoor OPV cells has a great potential in achieving higher photovoltaic performance.
关键词： indoor application,power conversion efficiency,organic photovoltaic cells,photostability
更新于2025-09-11 14:15:04
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Conjugation‐Curtailing of Benzodithionopyran‐Cored Molecular Acceptor Enables Efficient Air‐Processed Small Molecule Solar Cells
摘要： Small molecule solar cells (SMSCs) lag a long way behind polymer solar cells. A key limit is the less controllable morphology of small molecule materials, which can be aggravated when incorporating anisotropic nonfullerene acceptors. To fine-tune the blending morphology within SMSCs, a π-conjunction curtailing design is applied, which produces a efficient benzodithionopyran-cored molecular acceptor for nonfullerene SMSCs (NF-SMSCs). When blended with a molecular donor BDT3TR-SF to fabricate NF-SMSCs, the π-conjunction curtailed molecular acceptor NBDTP-M obtains an optimal power conversion efficiency (PCE) of up to 10.23%, which is much higher than that of NBDTTP-M of longer π-conjunction. It retains 93% of the PCE of devices fabricated in a glove box when all spin-coating and post-treating procedures are conducted in ambient air with relative humidity of 25%, which suggests the good air-processing capability of π-conjunction curtailed molecules. Detailed X-ray scattering investigations indicate that the BDT3TR-SF:NBDTP-M blend exhibits a blend morphology featuring fine interpenetrating networks with smaller domains and higher phase purity, which results in more efficient charge generation, more balanced charge transport, and less recombination compared to the low-performance BDT3TR-SF:NBDTTP-M blend. This work provides a guideline for molecular acceptors’ design toward efficient, low-cost, air-processed NF-SMSCs.
关键词： electron acceptors,all-small-molecule solar cells,air-processing,power conversion efficiency
更新于2025-09-11 14:15:04