Comparing different geometries for photovoltaic-thermoelectric hybrid devices based on organics

Coupling thermoelectrics (TE) with photovoltaics (PV) has emerged as an approach to solid-state solar harvesting, directly converting light and infrared heat into electricity. In this work, we compare PV-TE hybrid devices based on organic semiconductors in three different geometries: a reflection geometry, a non-contact transmission geometry, and a contact transmission geometry. The temperature rises of films of common organic thermoelectric materials, including poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), single-walled carbon nanotubes (swCNT), and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT), were measured in configurations representative of the proposed geometries. Because organic semiconductors possess broadband light absorption and low thermal conductivities, a significant rise in temperature was observed under illumination for all geometries. We find, however, that the best configuration is, in fact, the transmission contact mode because it sums two effects. Operating under 1 sun illumination, the temperature of a commercial organic PV module increased by ≈30 K, which leads to an enhancement in OPV performance compared to room temperature. After attaching a thermoelectric to the OPV module, losses from convection are reduced, and the OPV module heats up even more, further increasing its efficiency while additionally enabling thermoelectric generation. Finally, we calculate theoretical thermoelectric efficiencies for the materials and their respective power densities.The authors acknowledge financial support from the Spanish Ministry Science and Innovation through the “Severo Ochoa” Program for Centers of Excellence in R&D SEV-2015-0496 (FUNMAT) and CEX2019-000917-S (FUNFUTURE), and PGC2018-095411-B-I00 (RAINBOW) projects; from the Generalitat de Catalunya through grants 2017SGR488 and AGAUR 2018 PROD 00191; and from the European Research Council (ERC) under grant agreement no. 648901. This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 713673. J. P. J. has received financial support through the “la Caixa” INPhINIT Fellowship Grant for Doctoral studies at Spanish Research Centers of Excellence (Grant code: LCF/BQ/IN17/11620035), “la Caixa” Banking Foundation (ID100010434), Barcelona, Spain. O. Z. A. acknowledges CONACYT-SENER for his PhD scholarship (no. 472571). J. P. J. acknowledges the departments of Physics, Chemistry and Geology of the Autonomous University of Barcelona (UAB) as coordinators of the PhD programme in Materials Science. The authors thank Dr A. Roig, Dr A. Laromaine and Dr D. Abol-Fotouh (ICMAB-CSIC) for the CNT:cellulose sample preparation and fruitful discussions. The authors thank Dr Aleksandr Perevedentsev for his help with sample preparation, and Mr Pau Molet for his help with the FTIR measurements. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

Hybrid photovoltaic-thermoelectric devices based on organic semiconductors

En aquesta tesis, s'ha explorat el acoblament de generadors termoelèctrics (TEGs, per les seves sigles en anglès) a celes solars orgàniques (OSCs, per les seves sigles en anglès) en dispositius híbrids de estat sòlid per generació d'electricitat. En la primera part d'aquesta tesis s'ha demostrat la capacitat dels materials termoelèctrics (TE) orgànics per captar radiació solar i transformar-la en electricitat en un procés de dos passos. En un primer pas, la radiació solar es converteix en calor, motiu pel qual es van caracteritzar els materials TE com absorbent solars. Utilitzem la espectroscòpia Infraroja per la Transformada de Fourier (FTIR, per les seves sigles en anglès) per investigar les seves propietats òptiques i la termografia infraroja (IR) per investigar les seves propietats fototèrmiques. En un segon pas, el calor es converteix en electricitat mitjançant el efecte Seebeck. Típicament els materials TE s'investiguen en el context de la recuperació de calor residual, el qual ens va motivar a investigar els efectes secundaris associats a la llum en els paràmetres TE, es a dir, la conductivitat elèctrica i el coeficient Seebeck. A continuació, vam explorar els paràmetres geomètrics del dispositiu híbrid, tal com la longitud de la pota, i vam proposar diverses geometries planes pels generadors termoelèctrics solars orgànics (SOTEGs, per les seves sigles en anglès). El focus d'aquesta part eren els SOTEGs amb geometries planes, però vam comparar breument les geometries planes amb les verticals. Per últim, vam fabricar un dispositiu com a prova de concepte incorporant un mirall concentrador. En la segona part de la tesis, el focus es centra en investigar tres geometries de dispositiu diferents per acoblar un generador termoelèctric (TEG) a una OSC, recorrent a les dades experimentals obtingudes a partir dels espectres FTIR i de les imatges de termografia IR. Quan s'utilitza una cel·la solar semi-transparent en un dispositiu híbrid, el TEG pot fer us del calor generat i la llum transmesa per la cel·la solar. S'observa que la eficiència de conversió de potencia (PCE, per les seves sigles en anglès) de un mòdul comercial de OSC millora amb la temperatura. Motivats per la millora en la PCE observada en la segona part, vam investigar l'efecte de la temperatura en els paràmetres OSCs mitjançant les característiques J-V en funciço de la temperatura i de la intensitat de la llum. S'escull el sistema PBDB-T:ITIC per estudiar degut a la seva excel·lent estabilitat tèrmica. Un mètode d'alt rendiment, la tècnica del recobriment per fulla (Blade coating en anglès) s'utilitza per fabricar capes actives amb grosors variables. Per aquet sistema i uns altres tres, observem una millora amb la temperatura en la densitat de corrent de curtcircuit (JSC), el factor d'emplenat (FF, per les seves sigles en anglès) i la PCE. Combinant simulacions deriva-difusió (realitzades per un col·laborador) amb mesures de corrent limitada per carrega espacial (SCLS, en anglès) en funció de la temperatura, mesures d'eficiència externa quàntica en funció de la temperatura i tècniques de dispersió, concretament dispersió de rajos X de angle petit (GISAXS, per les seves sigles en anglès) i la dispersió de rajos X de angle ampli (GIWAXS, per les seves sigles en anglès), demostrem que la millora reversible en el rendiment del dispositiu es deu al transport de carregues per salt, que s'activa tèrmicament

Solar Harvesting: a Unique Opportunity for Organic Thermoelectrics?

Thermoelectrics have emerged as a strategy for solar‐to‐electricity conversion, as they can complement photovoltaic devices as IR harvesters or operate as stand‐alone systems often under strong light and heat concentration. Inspired by the recent success of inorganic‐based solar thermoelectric generators (STEGs), in this manuscript, the potential of benchmark organic thermoelectric materials for solar harvesting is evaluated. It is shown that the inherent properties of organic semiconductors allow the possibility of fabricating organic STEGs (SOTEGs) of extraordinary simplicity. The broadband light absorption exhibited by most organic thermoelectrics combined with their low thermal conductivities results in a significant temperature rise upon illumination as seen by IR thermography. Under 2 sun illumination, a temperature difference of 50 K establishes between the illuminated and the non‐illuminated sides of a poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) film, and ≈40 K for a carbon nanotube/cellulose composite. Moreover, when using light as a heat source, the Seebeck coefficient remains unaffected, while a small photoconductivity effect is observed in PEDOT:PSS and carbon nanotubes. Then, the effect of several geometrical factors on the power output of a solar organic thermoelectric generator is investigated, enabling us to propose simple SOTEG geometries that capitalize on the planar geometry typical of solution‐processable materials. Finally, a proof‐of‐concept SOTEG is demonstrated, generating 180 nW under 2 suns.The authors acknowledge financial support from the Spanish Ministry of Economy, Industry, and Competitiveness through the ‘‘Severo Ochoa'' Program for Centers of Excellence in R&D (SEV‐2015‐0496), MAT2015‐70850‐P and PGC2018‐095411‐B‐I00 projects; from the Generalitat de Catalunya through grants 2017SGR488 and AGAUR 2018 PROD 00191; from CSIC through project 201560I032; and from the European Research Council (ERC) under grant agreement no. 648901. This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska‐Curie grant agreement No. 713673. J.P.J. has received financial support through the “la Caixa” INPhINIT Fellowship Grant for Doctoral studies at Spanish Research Centers of Excellence (Grant code: LCF/BQ/IN17/11620035), “la Caixa” Banking Foundation (ID100010434), Barcelona, Spain. O.Z.A. acknowledges CONACYT‐SENER for his Ph.D. scholarship (No 472571). The authors thank Dr. Deyaa Abol‐Fotouh (ICMAB) for the CNT:cellulose sample preparation. The authors thank Dr. Anna Laromaine (ICMAB), Dr. Sebastian Reparaz (ICMAB), and Dr. Carlos Prieto (ICMM) for fruitful discussions. The authors also thank Mr. Martí Gibert Roca for his help with the 3D printer and Dr. Alexander Stangl for his help with the nanovoltmeter.Peer reviewe

o-Carborane-based fluorophores as efficient luminescent systems both as solids and as water-dispersible nanoparticles

This article is part of the themed collection: Boron Chemistry in the 21st Century: From Synthetic Curiosities to Functional MoleculesA set of o-carborane-appended π-conjugated fluorophores and their light-emitting properties in the solid state are reported. The aggregation-induced emission enhancement (AIEE) exhibited for one of the fluorenyl derivatives paved the way to successfully preparing o-carborane-containing organic nanoparticles (NPs) homogeneously dispersed in aqueous media that maintain their luminescence properties. Notably, NPs processed as thin films also show high fluorescence efficiency, suggesting potential optical and optoelectronic applications.This work was financially supported by MICINN (PID2019-106832RB-I00, PID2019-105622RB-I00 and the Severo Ochoa Program for Centers of Excellence for the FUNFUTURE CEX2019-000917-S project). S. S. acknowledges financial support from DOC-FAM, the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 754397. Z. K. is grateful for the general support of the Premium Postdoctoral Research Program 2019. We thank Dr Claudio Roscini from ICN2 for his kind help with the solid state luminescence measurements. Sohini Sinha is enrolled in the UAB PhD Program.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Heteroleptic Ruthenium(II) Complexes with 2,2′-Bipyridines Having Carbonitriles as Anchoring Groups for ZnO Surfaces: Syntheses, Physicochemical Properties, and Applications in Organic Solar Cells

Heteroleptic ruthenium (II) complexes were used for sensitizing ZnO surfaces in organic solar cells (OSCs) as mediators with photoactive layers. The complexes [Ru(4,4′-X2-bpy)(Mebpy-CN)2]2+ (with X = -CH3, -OCH3 and -N(CH3)2; bpy = 2,2′-bipyridine; Mebpy-CN = 4-methyl-2,2′-bipyridine-4′-carbonitrile) were synthesized and studied by analytical and spectroscopical techniques. Spectroscopic, photophysical, and electrochemical properties were tuned by changing the electron-donating ability of the -X substituents at the 4,4′-positions of the bpy ring and rationalized by quantum mechanical calculations. These complexes were attached through nitrile groups to ZnO as interfacial layer in an OSC device with a PBDB-T:ITIC photoactive layer. This modified inorganic electron transport layer generates enhancement in photoconversion of the solar cells, reaching up to a 23% increase with respect to the unsensitized OSCs. The introduction of these dyes suppresses some degradative reactions of the nonfullerene acceptor due to the photocatalytic activity of zinc oxide, which was maintained stable for about 11 months. Improving OSC efficiencies and stabilities can thus be achieved by a judicious combination of new inorganic and organic materials.Fil: Salomón, Fernando Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; ArgentinaFil: Vega, Nadia Celeste. Universidad Nacional de Tucumán. Instituto de Física del Noroeste Argentino. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Física del Noroeste Argentino; ArgentinaFil: Jurado, José Piers. Instituto de Ciencias de Materiales de Barcelona; EspañaFil: Moran Vieyra, Faustino Eduardo. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; ArgentinaFil: Tirado, Monica Cecilia. Universidad Nacional de Tucumán. Instituto de Física del Noroeste Argentino. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Física del Noroeste Argentino; ArgentinaFil: Comedi, David Mario. Universidad Nacional de Tucumán. Instituto de Física del Noroeste Argentino. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto de Física del Noroeste Argentino; ArgentinaFil: Campoy Quiles, Mariano. Instituto de Ciencias de Materiales de Barcelona; EspañaFil: Cattaneo, Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; ArgentinaFil: Katz, Néstor Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentin