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Chang, Y. C., Larrain, F. A., Fuentes-Hernandez, C., Park, Y., & Kippelen, B. (2023). Inverted organic tandem solar cells with a charge recombination stack employing spatially confined p-type electrical doping. J. Appl. Phys., 134(9), 095502.
Abstract: We report on the application of solution-based p-type electrical doping using 12-molybdophosphoric acid hydrate (PMA) to the fabrication of organic tandem solar cells. Such a doping approach leads to a spatially confined vertical doping profile down to a limited depth from the surface of polymer films, thus allowing the hole-collecting component of the charge recombination stack to be embedded in the photoactive layer of the bottom sub-cell. This simplifies the device architecture by removing the need for an extra dedicated hole-collecting layer. It is shown that this novel charge recombination stack comprising a PMA-doped bottom photoactive layer and a trilayer of Ag/AZO/PEIE is compatible with a solution-processed top photoactive layer. The fabricated inverted organic tandem solar cells exhibit an open-circuit voltage that is close to the sum of the open-circuit voltages of the individual sub-cells, and a fill factor that is close to the better fill factor of the two sub-cells.
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Chang, Y. C., Larrain, F. A., Fuentes-Hernandez, C., Park, Y., & Kippelen, B. (2024). Solution-based electrical doping of organic photovoltaics with non-fullerene acceptors facilitated by solvent vapor pre-treatment. AIP Advances, 14(1), 015247.
Abstract: Solution-based electrical doping of organic semiconductors using 12-molybdophosphoric acid (PMA) hydrate has been shown to allow p-type doping of conjugated polymers over a limited depth from the surface, enabling the fabrication of organic solar cells with a simplified device architecture. However, the doping level of certain conjugated polymers using PMA was found to be limited by the polymer film volume. Here, we report a modified PMA doping technique based on film volume expansion that is applicable to device fabrication, leading to hole-collecting layer-free non-fullerene organic photovoltaic devices, which exhibit a comparable photovoltaic performance to those with a commonly evaporated MoO3 hole-collecting layer. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).
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Larrain, F. A., Fuentes-Hernandez, C., Chang, Y. C. H., Rodriguez-Toro, V. A., Abraham, S., & Kippelen, B. (2021). Increasing Volume in Conjugated Polymers to Facilitate Electrical Doping with Phosphomolybdic Acid. ACS Appl. Mater. Interfaces, 13(19), 23260–23267.
Abstract: Molecular p-type electrical dopants have been proven useful to fine-tune the optoelectronic properties of bulk organic semiconductors and their interfaces. Here, the volume in polymer films and its role in solution-based electrical p-type doping using phosphomolybdic acid (PMA) are studied. The polymer film volume was controlled using two approaches. One is based on heating both the PMA solution and the film prior to immersion. The second is based on coating the polymer film with a liquid blend that contains the PMA solution and a swelling solvent. 31P NMR and FTIR experiments indicate that the Keggin structure appears to be preserved throughout the doping process. Results show that increasing the polymer volume facilitates the infiltration of the PMA Keggin structure, which results in an increased electrical p-type doping level.
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Walker, P., Nerenberg, R., Pizarro, G., Aybar, M., Pavissich, J. P., González, B., et al. (2024). Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment. Water Sci. Technol., Early Access.
Abstract: We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m(2)-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m(2)-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.
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