Molecular weight tuning of low bandgap polymers by continuous flow chemistry: increasing the applicability of PffBT4T for organic photovoltaics

Pirotte, Geert; Agarkar, Shruti; Xu, Bing; Zhang, Junxiang; Lutsen, Laurence; Vanderzande, Dirk; Yan, He; Pollet, Paméla; Reynolds, John R.; Maes, Wouter; Marder, Seth R.

doi:10.1039/c7ta05627c

Cited by 26 publications

(25 citation statements)

References 64 publications

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“…Beyond an influence on device operation, the intrinsic amorphous miscibility determines the stability of a morphology if the morphology has to be quenched inside the binodal (Figure b) for best performance. Of particular relevance to this subject are low bandgap poly(difluorobenzothiadiazole‐alt‐quaterthiophene) (PffBT4T) polymers (see Figure 7 a) such as PffBT4T‐2OD (also known as PCE11) and its derivatives. These PffBT4T polymers represent the best options for top performing polymer:fullerene devices and a class of high performance conjugated polymers with excellent power conversion efficiency over 10% in many fullerene and nonfullerene systems.…”

Section: Relating Miscibility To Device Functionmentioning

confidence: 99%

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Collins

Jiao

et al. 2018

Advanced Energy Materials

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donor:acceptor ratio, molecular weight, and processing parameters (annealing/ coating temperature, choices of co-solvent or solvent additive, solvent annealing, etc.) come into play in determining the final morphology of a PSC and thus key performance parameters, such as open-circuit voltage (V oc ), short-circuit current density (J sc ), and fill factor (FF). For a new photovoltaic polymer or a new donor:acceptor combination, new solvents and other processing conditions are usually empirically explored and optimized within a limited range of variables. Furthermore, there is currently no widely recognized conceptual framework that allows determining the best-matched acceptor material for a given donor polymer and only by carefully considering the influences of each parameter individually can these factors be exploited. All of these variables make it extremely challenging to predict the optimal BHJ morphology and performance of PSCs when designing and using new materials. [2,7,8,[11][12][13][14] In the BHJ of a PSC device, the polymeric electron donor (D) and organic electron acceptor (A) materials form a complex structure and morphology with the goal of optimizing simultaneously photon absorption, exciton separation, and charge transport. Generally, the disorder and semi-crystalline (sometimes nearly amorphous) qualities of the organic/polymeric photovoltaic materials make their blends difficult to form a simple two-phase morphology with pure aggregated donor and acceptor phases. [15] A three-phase morphology (see Figure 1a) including pure donor aggregates, pure acceptor aggregates, and amorphous intermixed portions (consisting of dispersed fullerene in the mostly amorphous polymer) has been previously observed or inferred by us and others in a wide range of PSC material systems. [16][17][18][19][20] Recent kinetic Monte Carlo simulations [21] have suggested that this three-phase morphology may be favorable as the electronic structure of both the donor and acceptor depends on the level of aggregation, thus providing an electronic landscape that can help to sweep out charges created in the mixed phases. Molecular dynamics simulations of a matrix of polymer:acene blends pointed to the significance of thermodynamic molecular interactions in determining the formation of BHJ morphologies. [14] Practically, these molecular interactions determine an upper limit of purity of the mixed phases in the blend films, [22] which will likely impact charge creation and recombination processes in devices. [13,17,23,24] Polymer solar cells (PSCs) continue to be a promising low-cost and lead-free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. U...

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Section: Relating Miscibility To Device Functionmentioning

confidence: 99%

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Collins

Jiao

et al. 2018

Advanced Energy Materials

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299

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“…[ 15‐21 ] The performance of BHJ PSCs relies strongly on the absorption of light in a wide range of wavelengths and the bicontinuous morphology for better electron and hole transportation. It is well‐known that the molecular weight of a D‐A conjugated polymer plays an important role in the absorption, morphology and photovoltaic performance of both polymer‐small molecule systems [ 22‐28 ] and polymer‐polymer systems. [ 29‐34 ] A number of studies have shown that the PCE improves with increasing molecular weight.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Tuning the Molecular Weight of Chlorine‐Substituted Polymer Donors for Small Energy Loss^†

Zhao

Wang

et al. 2021

Chin. J. Chem.

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The molecular weight of polymers plays a major role in their aggregation and miscibility in active layer, which eventually dominate the energy loss and device performance. A series of chlorine-substituted PBD-Cl polymers with controlled molecular weight have been synthesized as templates to discern a relationship between molecular weight and the optical properties, energy levels, morphologies, energy loss and photovoltaic performance. Although it has similar optical and electrochemical properties, when blended with acceptor N3, the low molecular weight polymer PBD-Cl L gives the biggest energy loss value, and a PCE of 12.06%. PBD-Cl H shows a moderate energy loss, but displays the lowest PCE of 9.00% as a result of excessive aggregation. PBD-Cl M with a medium molecular weight gives the smallest energy loss and achieves a PCE of 17.17%, which is among one of the highest values recorded to date for the Cl-substituted polymer solar cells. Moreover, the molecular weight mainly affects the nonradiative energy loss (ΔE 3 ), PBD-Cl M also shows the smallest value of 0.252 eV among three polymer donors. These results show the effect of controlling the molecular weight to achieve a small energy loss and provide guidelines which can lead to an understanding of the real photovoltaic performance of new materials.

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“…The key starting material for the synthesis of all three dyes is 6-bromo-2-diethylidene 1,3,3-trimethyl-3H-benzo[e]indolium-2yl 1,3,3-trimethyl indolinium-2yl-5-carboxy-iodide, S1 (see Scheme 2). The reaction of equimolar ratio of S1 with (4diphenylphospho)phenyl)ethynyl 7 in the presence of catalyst, Pd(OAc)2/PPh3,CuI/Et3N [45], The details of the synthesis of the three dyes are given in the Supplementary Materials. Here we only give a general description, as illustrated in Scheme 2.…”

Section: Materials-synthesis Of Oligomethine Cyanine Dyesmentioning

confidence: 99%

“…The key starting material for the synthesis of all three dyes is 6-bromo-2-diethylidene 1,3,3-trimethyl-3H-benzo[e]indolium-2yl 1,3,3-trimethyl indolinium-2yl-5-carboxy-iodide, S1 (see Scheme 2). The reaction of equimolar ratio of S1 with (4-diphenylphospho)phenyl)ethynyl 7 in the presence of catalyst, Pd(OAc)2/PPh3,CuI/Et3N [45], afforded the OMCD 1 dye. Reaction of equimolar amount of S1 and 7-(4-diphenylphosho)phenyl)ethynyl-3-yne-phenothiazine, S2, according to the literature [46] lead to OMCD 2.…”

Section: Materials-synthesis Of Oligomethine Cyanine Dyesmentioning

confidence: 99%

Photoexcitation Processes in Oligomethine Cyanine Dyes for Dye-Sensitized Solar Cells—Synthesis and Computational Study

et al. 2020

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We report density functional theory (DFT) calculations of three newly synthesized oligomethine cyanine-based dyes as potential TiO2-sensitizers in dye-sensitized solar cells. The three dyes have π-symmetry and the same acceptor side, terminating in the carboxylic anchor, but they differ through the π-bridge and the donor groups. We perform DFT and time-dependent DFT studies and present the electronic structure and optical properties of the dyes alone as well as adsorbed to the TiO2 nanocluster, to provide some predictions on the photovoltaic performance of the system. We analyze theoretically the factors that can influence the short circuit current and the open circuit voltage of the dye-sensitized solar cells. We examine the matching of the absorption spectra of the dye and dye-nanocluster system with the solar irradiation spectrum. We display the energy level diagrams and discuss the alignment between the excited state of the dyes and the conduction band edge of the oxide as well as between the redox level of the electrolyte and the ground state of the dyes. We determine the electron density of the key molecular orbitals and analyze comparatively the electron transfer from the dye to the semiconducting substrate. To put our findings in the right perspective we compare the results of our calculations with those obtained for a coumarin-based dye used in fabricating and testing actual devices, for which experimental data regarding the photovoltaic performance are available.

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Molecular weight tuning of low bandgap polymers by continuous flow chemistry: increasing the applicability of PffBT4T for organic photovoltaics

Abstract: Molecular weight tuning of a prototype OPV low bandgap polymer, PffBT4T (PCE-11), by continuous flow chemistry.

Cited by 26 publications

References 64 publications

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Tuning the Molecular Weight of Chlorine‐Substituted Polymer Donors for Small Energy Loss^†

Photoexcitation Processes in Oligomethine Cyanine Dyes for Dye-Sensitized Solar Cells—Synthesis and Computational Study

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Molecular weight tuning of low bandgap polymers by continuous flow chemistry: increasing the applicability of PffBT4T for organic photovoltaics

Abstract: Molecular weight tuning of a prototype OPV low bandgap polymer, PffBT4T (PCE-11), by continuous flow chemistry.

Cited by 26 publications

References 64 publications

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Miscibility–Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation

Tuning the Molecular Weight of Chlorine‐Substituted Polymer Donors for Small Energy Loss†

Photoexcitation Processes in Oligomethine Cyanine Dyes for Dye-Sensitized Solar Cells—Synthesis and Computational Study

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Product

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Tuning the Molecular Weight of Chlorine‐Substituted Polymer Donors for Small Energy Loss^†