We present a method to dissolve carbon nanotubes that simultaneously allows to prepare n-doped films. These films are composed of thinner bundles of longer tubes when compared to films prepared using surfactants and sonication. Their negative Seebeck coefficient and high electrical conductivity make them good candidates for thermoelectric applications. We investigate their stability in air by aging them at elevated temperatures, showing stabilities over 500 h, which is further improved by the use of crown ethers. Finally, we demonstrate the usefulness of the prepared materials by fabricating an organic thermoelectric generator comprising 40 legs. ; The authors acknowledge financial support from the Spanish Ministry of Science and Innovation through the "Severo Ochoa" Program for Centers of Excellence in R&D (No. CEX2019-000917-S), Nos. PGC2018-095411-B-I00 and MAT2017-90024-P (TANGENTS)-EI/FEDER; from the Generalitat de Catalunya and European Union (FEDER) through AGAUR 2018 PROD 00191; and from the European Research Council (ERC) under Grant Agreement No. 648901. We also thank Professor Alejandro R. Goñi (ICMAB) for fruitful discussions. ; Peer reviewed
Cesium lead halide perovskite nanocrystals have emerged as one of the most promising candidates for manufacturing portable lasers and light sources. In order to harness and exploit their photoluminescence more effectively, the nanocrystals are often accompanied by a photonic scheme that improves light emission. In this work, one introduces a quasi-3D photonic crystal composed of a 2D-grating on top of a distributed Bragg reflector (DBR) that provides a greater photoluminescence enhancement than the isolated architectures alone. The quasi-3D photonic crystals support both Rayleigh-Wood anomalies and guided modes that populate the photonic bandgap of the Bragg mirror, all of them capable of enhancing the outcoupling of light from the emitting layer. In order to demonstrate the benefits of the quasi-3D system, one prepares 2D-gratings, DBRs, and quasi-3D photonic crystals covered with metal halide perovskite nanocrystals and studies the photoluminescence enhancement produced in each case. Interestingly, the quasi-3D structure exhibits a photoluminescence enhancement of 16 times and an increase in spontaneous emission rate, greatly exceeding the values observed for the separate components. ; This project was received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 637116, Enlightment), the Generalitat de Catalunya (2017-SGR-00488), and the Spanish Ministerio de Ciencia e Innovación through grants PID2019-106860GB-I00, PID2020-119777GB-I00 and CEX2019-000917-S (FUNFUTURE) in the framework of the Spanish Severo Ochoa Centre of Excellence program. L.P. acknowledges the support from the Spanish Ministerio de Ciencia e Innovación through Ramón y Cajal grant (RYC2018-026103-I). J.M.C. acknowledges an FPI fellowship (PRE2020-09411) from MICINN cofinanced by the European Social Fund and the Ph.D. program in Materials Science from Universitat Autònoma de Barcelona. ; Peer reviewed
A combinatorial study of the effect of in-mixing of various guests on the thermoelectric properties of the host workhorse polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) is presented. Specifically, the composition and thickness for doped films of PBTTT blended with different polymers are varied. Some blends at guest weight fractions around 10–15% exhibit up to a fivefold increase in power factor compared to the reference material, leading to zT values around 0.1. Spectroscopic analysis of the charge-transfer species, structural characterization using grazing-incidence wide-angle X-ray scattering, differential scanning calorimetry, Raman, and atomic force microscopy, and Monte Carlo simulations are employed to determine that the key to improved performance is for the guest to promote long-range electrical connectivity and low disorder, together with similar highest occupied molecular orbital levels for both materials in order to ensure electronic connectivity are combined. ; The authors acknowledge financial support from the Spanish Ministry of Science and Innovation through the Severo Ochoa" Program for Centers of Excellence in R&D (No. CEX2019-000917-S) and projects PGC2018-095411- B-I00, PGC2018-094620-A-I00, and MAT2017-90024-P (TANGENTS)-EI/Fondo Europeo de Desarrollo Regional and from the European Research Council (ERC) under Grant Agreements Nos. 648901 and 963954. J.M. thanks Ministerio de Ciencia, Innovación y Universidades for the Ramón y Cajal contract. The authors are thankful to Dr. Agustín Mihi for access and support with the FTIR equipment. The authors acknowledge the European funding (European Regional Development Fund and European Social Fund). The authors thank Andrés Gómez Rodríguez from the Scanning Probe Microscopy Laboratory (ICMAB-CSIC) for a set of fine AFM measurements. GIWAXS experiments were performed at NCD-SWEET beamline at ALBA Synchrotron with the collaboration of ALBA staff. Finally, the authors acknowledge the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unidad de Recursos de Información Científica para la Investigación (URICI). M.K. thanks the Carl Zeiss Foundation for financial support. G.Z. acknowledges the support from Alexander von Humboldt Foundation. ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed
