26 research outputs found
Solution Processed Bathocuproine for Organic Solar Cells
No full textPublisher Copyright: © 2017 IEEE.PTB7/PC71BM bulk heterojunction solar cell devices where the conventional calcium hole-blocking layer has been replaced by a solution processed bathocuproine (BCP) layer is described. The BCP thin film was deposited via spin coating from a dilute solution of BCP in a mixture of toluene and methanol directly on the top of the active layer. The silver cathode was subsequently deposited via thermal evaporation. The study shows that solar cells devices comprising solution-processed BCP show similar performance than devices made from either calcium or evaporated BCP. Moreover, the devices made from solution-processed BCP show superior stability in air than calcium and evaporated BCP-based devices. This is to the best of our knowledge, the first report of the use of solution processed BCP in organic solar cells.Manuscript received July 26, 2017; revised October 20, 2017; accepted November 28, 2017. Date of publication December 4, 2017; date of current version January 8, 2018. This work was supported by the Spanish Ministry of Economy and Competitiveness under Grant TEC2015-71915-REDT and Grant TEC2015-71324-R (MINECO/FEDER), in part by the Departa-ment d’Innovació, Universitats i Empresa, Generalitat de Catalunya (AGAUR) 2017SGR1527, and in part by the ICREA under the 2014 ICREA Academia Award. The review of this paper was arranged by Associate Editor C. Anghel. (Corresponding author: Lluis F. Marsal.) C. Stenta, M. P. Montero-Rama, A. Viterisi, and L. F. Marsal are with the De-partament d’Enginyeria Electrònica, Elèctrica i Automàtica, Universitat Rovira i Virgili, Tarragona 43007, Spain (e-mail: [email protected]; [email protected]; [email protected]; [email protected]).Peer reviewe
Crystallinity and Molecular Packing of Small Molecules in Bulk-Heterojunction Organic Solar Cells
No full textInternational audienceCrystallinity has played a major role in organic solar cells (OSCs). In small molecule (SM) bulk-heterojunction (BHJ) OSCs, the crystallinity and crystalline packing of SM donors have been shown to have a dramatic impact on the formation of an optimum microstructure leading to high-power conversion efficiency (PCE). Herein we describe how crystallinity differs from polymers to SMs, and how the packing habits of SMs (particularly donors) in active layers of BHJ devices can be described as following two different main modes: a single crystal-like and a liquid crystal-like packing type. This notion is reviewed from a chronological perspective, emphasising milestone donor structures and studies focusing on the crystallinity in SM-BHJ OSCs. This review intends to demonstrate that a shift towards a liquid crystalline-like packing can be identified throughout the history of SM-BHJ, and that this shift can be associated with an increase in overall PC
Self‐Assembly‐Induced Colloidal Covalent Organic Frameworks Toward Photocatalytic H 2 Evolution: A Surfactant‐Free Concept
No full textInternational audienceCovalent Organic Frameworks (COFs) are promising materials for photocatalytic applications due to their tunable optoelectronic properties. However, their rapid precipitation in solution limits their processability and functionality. In this study, the new concept of Self‐Assembly‐Induced Colloidal COFs SAI2COF is investigated by in situ stabilization of a donor‐acceptor TtaTpa COF with a macromolecular blocking agent, i.e., Poly(2‐(DiMethylAmino)Ethyl Methacrylate) (PDMAEMA), to control particle morphology, dispersion, and colloidal stability. Three synthesis strategies are explored to introduce the blocking agent at different stages of COF formation. Kinetic monitoring via UV–vis spectroscopy demonstrated that PDMAEMA slows COF growth, delaying precipitation while preserving crystallinity and light absorption properties. Morphological analyses revealed that stabilization strategies significantly influence particle surface characteristics, yielding colloidally stabilized COFs. Aqueous redispersion experiments confirmed that COFs synthesized via these strategies can be stabilized in a water medium. This approach offers an original surfactant‐free pathway toward the development of stable colloidal COFs for photocatalytic hydrogen production
Porphyrin-silver acetylide cluster catalysts with dual active sites for the electrochemical reduction of CO 2
No full textInternational audience2D-like porphyrin-silver acetylide clusters synthesised from tetra alkyne-substituted porphyrins with high faradic efficiency towards the electroreduction of CO 2 to CO
Joule-Heating Annealing to Increase Organic Solar Cells Performance: A Comparative Study
No full textIn this work, we present our results on the influence of post-deposition treatments on the morphology and optical properties of photoactive films made of small molecules and their subsequent effect on the performance of photovoltaic (PV) devices. We have chosen DPP(TBFu)2:PC61BM as a benchmark model system and compared a novel joule-heating annealing (JHA) treatment with the widely used temperature annealing (TA) and solvent annealing (SVA) treatments. Detailed characterization of the morphology of the active layer and the performance of the devices suggests that JHA is a valuable post-treatment technique that provides fast information about the development of domains in the photoactive layer. Finally, in this context, solar cells on flexible indium tin oxide (ITO) substrates, made of polyethylene terephthalate (PET), were fabricated and analyzed
Solvent Annealing Control of Bulk Heterojunction Organic Solar Cells with 6.6% Efficiency Based on a Benzodithiophene Donor Core and Dicyano Acceptor Units
No full textSolution processed organic solar cells based on A– D–D0–D–A small molecule with benzo[1,2-b:4,5-b0] dithiophene donor (D0) unit, cyclopentadithiophene
No full text Solution processed small molecule A–D–D0–D–A, denoted as BDT(CDTRH)2, consists of 2-ethylhexoxy substituted BDT (donor D' unit) as the central building block and 3-ethylrhodanine (RH) as the end capped terminal (acceptor group) unit, with a p-linkage of cyclopentadithiophene (CDT) (donor D). We have designed and synthesized it, and we have investigated its optical and electrochemical properties, finding that its energy levels are compatible with the energy levels of fullerene derivatives for efficient exciton dissociation. This small molecule has been used as an electron donor along with PC71BM as the electron acceptor for the fabrication of solution processed small molecule bulk heterojunction (BHJ) solar cells. The BHJ solar cell processed with BDT(CDTRH)2 : PC71BM (1 : 1 wt ratio) showed a power conversion efficiency (PCE) of 4.58% with Jsc ¼ 8.66 mA cm_x0002_2, Voc ¼ 0.98 V and FF ¼ 0.54. The high Voc value of the device has been attributed to the deeper HOMO energy level of BDT(CDTRH)2. The overall PCE of the device has been increased up to 6.02% (Jsc ¼ 10.42 mA cm_x0002_2, Voc ¼ 0.94 V FF ¼ 0.62) when the blend was processed with 3% v/v CN/CF solvent. This increase is mainly due to an increase in Jsc and FF, which was linked to the increase in crystallinity and favorable nanomorphology of the active layer improving exciton dissociation and achieving a more balanced charge transport in the device.</div
Structure–property relationship of atomically-precise silver acetylide clusters in the electroreduction of CO 2
No full textInternational audienceThe synthesis of a library of silver acetylide cluster catalysts for the electroreduction of CO2 is described. The methodology relies on a one-step reaction between terminal alkynes and an aqueous silver ammoniacal solution, producing a library of clusters isolated via simple filtration. Their catalytic properties in the CO2 electroreduction reaction were thoroughly assessed, focussing on faradaic efficiency, overpotential, turnover frequency and their structural features characterised via powder XRD, XPS and electrochemical methods. It was found that the chemical structure of the ligand had a strong impact on the overall crystallinity of the cluster, and a correlation between crystallinity, overpotential and selectivity was established. Our study points to the importance of the number of Ag(0) active sites formed under reducing conditions, which are directly linked to the ligand chemical structure, while the overpotential and selectivity are rather dictated by the degree of order (crystallinity) of the whole cluster
