Browsing by Author "Montero-Alejo, Ana L."

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    Effective Interfaces between Fullerene Derivatives and CH3NH3PbI3 to Improve Perovskite Solar Cell Performance
    (2023) Montero-Alejo, Ana L.; Barria-Caceres, Felipe; Lodeiro, Lucas; Menendez-Proupin, Eduardo
    Inverted hybrid perovskite solar cells using fullerene derivatives as an electron transport layer show high energy photo conversion efficiency and improvements in stability. In practice, a wide variety of fullerene derivative functional groups have been proposed, but there is still no clear understanding of the influence of this structure on solar cell behavior. Using density functional theory calculations, we study the conditions that allow the transport of electrons without energetic barriers in the interface formed between the surfaces of CH3NH3PbI3 and the derivatives of fulleropyrrolidine and PCBM. Representative atomistic models of the interfaces are provided, and the self-consistent electronic structures obtained with hybrid functionals were analyzed. It is shown that only the perovskite surface terminated in a layer rich in methylammonium iodide offers electron transport without energy barriers for fullerene derivatives. Moreover, the lead iodide (PbI2)-terminated surface is not passivated with fullerene derivatives. The surface state disappears if the PbI2-terminated surface is treated with ammonium salts or zwitterionic compounds, such as methylammonium chloride and sulfamic acid. Therefore, these modified surfaces favor the performance of the solar cells if the interfaces remain aligned, without barriers, for the transport of electrons. Our study offers these interface models to contribute to the optimal design of perovskite solar cells.
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    Polymers of intrinsic microporosity containing aryl-phthalimide moieties: synthesis, modeling, and membrane gas transport properties
    (2023) Rodriguez-Gonzalez, Fidel E.; Soto, Cenit; Palacio, Laura; Montero-Alejo, Ana L.; Escalona, Nestor; Schott, Eduardo; Comesana-Gandara, Bibiana; Terraza, Claudio A.; Tundidor-Camba, Alain
    High-performance polymers for membrane gas separation require the careful design of the structure-porous relationship. In this work, five phthalimide-based polymers of intrinsic microporosity (PIMs) were obtained via the double nucleophilic aromatic substitution with the commercially available 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane (TTSBI) monomer. The phthalimide monomers were synthesized considering different sizes and positions of the alkyl-substituents to evaluate their influence on the physical properties of the polymers and their potential use as gas separation membranes. Four polymers were soluble in the low-boiling solvents chloroform and tetrahydrofuran, facilitating the casting of self-standing films to evaluate their gas separation properties. The thermally stable membranes showed 5% weight lost between 537 ? and 549 ?. As powders, these four polymers showed apparent BET surface areas ranging from 434 to 661 m(2) g(-1). The experimental BET surface areas correlated with those obtained by molecular simulation models of the synthesized polymers. A linear function is proposed as a tool to predict, with a known uncertainty, the surface area values of this type of polymer from the corresponding computational models. As a trend, increasing the volume of the ortho-substituent in the aryl-phthalimide group increases the permeability of the membranes, reaching generally better performances than Matrimid (R) and close to those of PIM-1, considering their place on the Robeson diagrams of the O-2/N-2, CO2/CH4 and CO2/N-2 gas pairs. Aging studies between 63 and 122 days showed a decrease in permeability, accompanied by the typical increase in selectivity that tends to move the data parallel to the upper Robeson limits.