Morphological and micro-structural interface characterization in multilayer inverted polymer-fullerene bulk heterojunction solar cells

Inverted polymer solar cells based on P3HT/PCBM bulk heterojunction were prepared on flexible polyethylene naphthalate (PEN) substrate. The effect of annealing of the PEN/ITO/ZnO multilayer and ZnO/P3HT:PCBM on the structural, morphological, photophysical and photovoltaic properties was investigated and scrutinized directly on the OPV devices using atom probe tomography (APT), scanning electron microscopy (SEM) and microfocus X-ray techniques. We carried out a 3D reconstruction of the interfaces of the multilayer containing PEN/ITO, ZnO/ITO and P3HT:PCBM/ZnO to address the interface micro-structure and its influence on the morphology of the photoactive film. The analyses show that the morphology of the interfaces is affected by the structure of each layer of the BHJ devices causing orientation of P3HT crystals with PCBM aggregates and ZnO, which in turn leads to a significant change of the charge transport across each layer and therefore photovoltaic performances

Equivalent circuit and calculation of unbalanced power in three-wire three-phase linear networks

[EN] For analysis of three-wire three-phase linear systems, the transformations wye-delta and delta-wye from theorem of Kennelly are used. These transformations can be applied to balanced systems but not to unbalanced systems. This is due to the fact that zero-sequence voltages or zero-sequence currents are present in these types of connections. This modifies the value of the unbalance power in the load with respect to the generator. These zero-sequence voltages and currents that appear in generators and loads are not transferred over the network. The zero-sequence voltage in a delta-connected load and the zero-sequence current that is obtained using theorem of Kennelly in a star-connected load, or vice versa, cause different imbalance effects. Here, the equivalent circuit for any point of the system is developed. The impedances of the equivalent circuit in any node are calculated using line-to-line voltages and line currents. This equivalent circuit incorporates all energetic phenomena, including the unbalance of all downstream loads. For its verification, the phasor unbalance power is used.Montoya-Mira, R.; Diez-Aznar, J.; Blasco Espinosa, PA.; Montoya Villena, R. (2018). Equivalent circuit and calculation of unbalanced power in three-wire three-phase linear networks. IET Generation Transmission & Distribution. 12(7):1466-1473. https://doi.org/10.1049/iet-gtd.2017.0670S14661473127Emanuel, A. E. (1993). On the definition of power factor and apparent power in unbalanced polyphase circuits with sinusoidal voltage and currents. IEEE Transactions on Power Delivery, 8(3), 841-852. doi:10.1109/61.252612Jeon, S.-J. (2005). Definitions of Apparent Power and Power Factor in a Power System Having Transmission Lines With Unequal Resistances. IEEE Transactions on Power Delivery, 20(3), 1806-1811. doi:10.1109/tpwrd.2005.848658Czarnecki, L. S. (1994). Misinterpretations of some power properties of electric circuits. IEEE Transactions on Power Delivery, 9(4), 1760-1769. doi:10.1109/61.329509Willems, J. L. (2004). Reflections on Apparent Power and Power Factor in Nonsinusoidal and Polyphase Situations. IEEE Transactions on Power Delivery, 19(2), 835-840. doi:10.1109/tpwrd.2003.823182Emanuel, A. E. (1999). Apparent power definitions for three-phase systems. IEEE Transactions on Power Delivery, 14(3), 767-772. doi:10.1109/61.772313Jayatunga, U., Ciufo, P., Perera, S., & Agalgaonkar, A. P. (2015). Deterministic methodologies for the quantification of voltage unbalance propagation in radial and interconnected networks. IET Generation, Transmission & Distribution, 9(11), 1069-1076. doi:10.1049/iet-gtd.2014.0661Von Jouanne, A., & Banerjee, B. (2001). Assessment of voltage unbalance. IEEE Transactions on Power Delivery, 16(4), 782-790. doi:10.1109/61.956770Viswanadha Raju, G. K., & Bijwe, P. R. (2008). Efficient reconfiguration of balanced and unbalanced distribution systems for loss minimisation. IET Generation, Transmission & Distribution, 2(1), 7. doi:10.1049/iet-gtd:20070216Kersting, W. H. (2001). Causes and effects of unbalanced voltages serving an induction motor. IEEE Transactions on Industry Applications, 37(1), 165-170. doi:10.1109/28.903142Pillay, P., & Manyage, M. (2006). Loss of Life in Induction Machines Operating With Unbalanced Supplies. IEEE Transactions on Energy Conversion, 21(4), 813-822. doi:10.1109/tec.2005.853724Emanuel, A. E. (1998). The Buchholz-Goodhue apparent power definition: the practical approach for nonsinusoidal and unbalanced systems. IEEE Transactions on Power Delivery, 13(2), 344-350. doi:10.1109/61.660900Leon-Martinez, V., Montanana-Romeu, J., & Palazon-Garcia, J. M. (2011). Unbalance Compensator for Three-Phase Industrial Installations. IEEE Latin America Transactions, 9(5), 808-814. doi:10.1109/tla.2011.6030993Reginatto, R., & Ramos, R. A. (2014). On electrical power evaluation in dq coordinates under sinusoidal unbalanced conditions. IET Generation, Transmission & Distribution, 8(5), 976-982. doi:10.1049/iet-gtd.2013.0532Diez, J. M., Blasco, P. A., & Montoya, R. (2016). Formulation of phasor unbalance power: application to sinusoidal power systems. IET Generation, Transmission & Distribution, 10(16), 4178-4186. doi:10.1049/iet-gtd.2016.0730Marzband, M., Moghaddam, M. M., Akorede, M. F., & Khomeyrani, G. (2016). Adaptive load shedding scheme for frequency stability enhancement in microgrids. Electric Power Systems Research, 140, 78-86. doi:10.1016/j.epsr.2016.06.03

Experimental and theoretical investigation of ligand effects on the synthesis of ZnO nanoparticles

ZnO nanoparticles with highly controllable particle sizes(less than 10 nm) were synthesized using organic capping ligands in Zn(Ac)2 ethanolic solution. The molecular structure of the ligands was found to have significant influence on the particle size. The multi-functional molecule tris(hydroxymethyl)-aminomethane (THMA) favoured smaller particle distributions compared with ligands possessing long hydrocarbon chains that are more frequently employed. The adsorption of capping ligands on ZnnOn crystal nuclei (where n = 4 or 18 molecular clusters of(0001) ZnO surfaces) was modelled by ab initio methods at the density functional theory (DFT) level. For the molecules examined, chemisorption proceeded via the formation of Zn...O, Zn...N, or Zn...S chemical bonds between the ligands and active Zn2+ sites on ZnO surfaces. The DFT results indicated that THMA binds more strongly to the ZnO surface than other ligands, suggesting that this molecule is very effective at stabilizing ZnO nanoparticle surfaces. This study, therefore, provides new insight into the correlation between the molecular structure of capping ligands and the morphology of metal oxide nanostructures formed in their presence

Electrical Transport in “Few-Layer Graphene” Film Prepared by the Hot-Spray Technique: The Effect of Thermal Treatment

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