Examinando por Autor "Ramos, M. Mar"

Mostrando 1 - 4 de 4

Comparing the microstructure and photovoltaic performance of 3 perylene imide acceptors with similar energy levels but different packing tendencies
(Royal Society of Chemistry, 2022) Adel, Rana; Gala, Elena; Alonso-Navarro, Matías J.; Gutierrez-Fernandez, Edgar; Martín, Jaime; Stella, Marco; Martinez-Ferrero, Eugenia; de la Peña, Alejandro; Harbuzaru, Alejandra; Ramos, M. Mar; Ponce Ortíz, Rocío; Segura, José L.; Campoy-Quiles, Mariano
While it is widely recognized that microstructure plays an important role in the performance of organic photovoltaics (OPV), systematic studies are often challenging, as varying the molecular packing through typical chemical means (such as sidechain tuning) often affects the molecular energy levels, thus preventing a clear correlation. In this work we present the synthesis of three perylene imide (PI) based electron acceptors with almost identical energy levels, but distinct packing tendencies. We confirm our initial hypothesis by measuring solution and solid-state absorption, and cyclic voltammetry as well as characterizing the films by grazing incidence wide angle X-ray scattering (GIWAXS). In a second step, we repeat the characterization of the three materials in blends with two polymer donors, namely PCDTBT or PBDBT, whose energy levels are well aligned with those of the PI acceptors, and which, additionally, exhibit different degrees of structural order. We show how the initial strong difference between acceptors is partially blurred in blends, but still critical. Finally, we correlate our structural data with OPV devices made with the corresponding six blends. Our data suggest that a good donor acceptor marriage should ensure good energy alignment but also exhibit complementary crystallization tendencies of the two components.
Effective interplay of donor and acceptor groups for optoelectronic properties tuning in Oligothiophene-Naphtalimide Assemblies
(The Royal Society of Chemistry, 2020) Alonso-Navarro, Matías J.; Harbuzarub, Alexandra; de Echegaraya, Paula; Arrechea-Marcos, Iratxe; Harillo-Baños, Albert; de la Peña, Alejandro; Ramos, M. Mar; López Navarrete, J. Teodomiro; Campoy-Quiles, Mariano; Ponce Ortiz, Rocío; Segura, José L.
In this work, a series of naphthalimide fused thienopyrazine derivatives was designed, and their synthesis and characterization are reported herein. The interaction of this building block with a donor terthiophene fragment laterally substituted by a series of donor and acceptor constituents was analyzed in depth. This strategy was proven to efficiently modulate both the energy and topology of the frontier molecular orbitals involved in the charge transport mechanism. The interplay between the donor and acceptor strengths of the different units composing the material structure is thus essential to efficiently modulate charge carriers and transport properties and to finely tune the optical and electronic structures of the presented organic semiconductors
Synthesis and electronic properties of nitrogen-doped π-extended polycyclic aromatic dicarboximides with multiple redox processes
(The Royal Society of Chemistry, 2021) Alonso-Navarro, Matías J.; Harbuzaru, Alexandra; Martínez-Fernández, Marcos; Pérez Camero, Paula; López Navarrete, Teodomiro; Ramos, M. Mar; Ponce Ortíz, Rocío; Segura, José L.
In this work, a series of nitrogen-doped polycyclic aromatic mono and dicarboximides was designed, and their synthesis is reported by an innovative synthetic procedure that avoids metal-based crosscoupling reactions. A combined theoretical, electrochemical, optical spectroscopy and material characterization study allows the investigation of the interplay of different effects such as (i) the type of solubilizing chain, (ii) the all-acceptor vs. donor–acceptor nature of the novel systems, and (iii) the molecular ordering, on the ability to stabilize multiple charges and on the OTFT device response characteristics. The amphoteric redox behavior of some of the novel systems allow to obtain ambipolar mobilities while the electron mobility values of the three all-acceptor systems can be rationalized in terms of supramolecular aggregation and enhanced film-forming ability.
Tunable electroactive oligothiophene-naphthalimide semiconductors via end-capped engineering: Cumulative effects beyond the linker
(Royal Society of Chemistry, 2023) Alonso-Navarro, Matías J.; Harbuzaru, Alexandra; Gonzalez- Nuñez, Raúl; Ramos, M. Mar; Segura, José L.; Ponce Ortíz, Rocío
Aiming to obtain novel functional semiconducting materials for their use in organic electronics, the combination of strong donor moieties with electron-withdrawing units is one of the most useful strategies to obtain ambipolar semiconductors with tunable properties. Nowadays most of the efforts headed to efficient materials are based on small changes in the alkyl pendant chains or by replacing single atoms. However, a precise design of new functional materials is still challenging. For this reason, in this work we present a new synthetic approach for achieving redox amphoteric organic semiconductors by tuning their opto-electrochemical properties via rational chemical modifications. All these materials present low-lying LUMO levels, lower than 4.00 eV with broad absorption up to 800 nm in the UV-Vis-NIR spectra. In addition, they have been characterized by DFT, absorption and Raman vibrational spectroscopies, while their charge stabilization abilities are studied by means of spectroelectrochemical techniques. The results point out to a quite complex electronic scenario that goes beyond the expected cumulative effects of the independent molecular units constituting the final molecular assembly.