A Systematic Approach to Solvent Selection Based on Cohesive Energy Densities in a Molecular Bulk Heterojunction System

Walker, Bright; Tamayo, Arnold; Duong, Duc T.; Dang, Xuan‐Dung; Kim, Chun Ki; Granstrom, Jimmy; Nguyen, Thuc‐Quyen

doi:10.1002/aenm.201000054

Cited by 176 publications

(152 citation statements)

References 35 publications

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“…[ 2,18,27,28 ] Among these, using solvent mixtures and additives is often the most effective optimization strategy to get improved effi ciency for a given material system. [ 5,25,[29][30][31] Expanding the canonical two-phase paradigm, complex three-phase, hierarchical morphologies including pure fullerene aggregates, pure polymer aggregates, and a mixed phase, which is thought to consist of dispersed fullerene in mostly amorphous polymer, have been observed or inferred in several cases. [ 5,8,[32][33][34][35] This has caused a re-evaluation of the actual morphologies, initiated by the observation of miscibility of fullerene in many donor polymers.…”

Section: Doi: 101002/adma201400216mentioning

confidence: 98%

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells

et al. 2014

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Section: Doi: 101002/adma201400216mentioning

confidence: 98%

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells

et al. 2014

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“…This is a problem when the solubility parameter is used to compare molecules with substantially different sizes. Although the solubility parameter concept has already been introduced in the field of PSC, 34,35 the effect of volume is seldom taken into consideration.…”

Section: Discussionmentioning

confidence: 99%

Effect of Drying Time on Morphology and Photovoltaic Characteristics of Polymer Solar Cells of Bis-PCBM/P3HT Composites

Nagai

Gao

Huang

et al. 2016

ECS J. Solid State Sci. Technol.

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Slow drying has been proposed as a way to improve the performance of polymer solar cells (PSCs) where the drying time for the coated films is increased using a condensed solvent vapor atmosphere. This work investigated the slow drying mechanism by using PSCs consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and bis-[6,6]-phenyl-C61-butyric acid methyl ester (bis-PCBM) and focusing on the phase-separated morphology of bulk heterojunction films. With conventional spin casting, the power conversion efficiency (PCE) of the cells was very low (0.83%). The application of slow drying resulted in notable improvements in the short-circuit current density (5.85 → 8.07 mA/cm 2 ) and fill factor (0.12 → 0.55). Optimization of the thermal annealing and cathode interfacial conditions resulted in a high PCE of 4.05%. As the drying time was increased, the P3HT domains changed from connected band-like shapes to small separated ball-like shapes. The mechanism for this effect of slow drying on the bis-PCBM/P3HT cell characteristics is understood as follows: The slow drying causes the P3HT domains to separate into small pieces, which causes the area of the p−n interfaces to increase, resulting in an increase in free carrier generation and increased the short-circuit current density of PSCs. Organic photovoltaics have been actively studied as a major candidate for use in next-generation solar cells due to the several advantages they possess, including light weight, thin film, and low material cost.1-3 In particular, polymer solar cells (PSCs) can be made by applying a solution of p-type polymers and n-type fullerene-based small molecules, meaning that PSCs do not require expensive vacuum equipment, which can potentially reduce processing costs. The efficiency of PSCs has been drastically improved over the past decade. A cell efficiency of more than 10% has already been reported. 4 However, further improvement in efficiency is crucial for practical use.The performance of PSCs depends not only on the materials used but also their processing conditions. Thermal annealing 5-8 and solvent annealing 9-11 are representative techniques for improving solar cell performance. These methods have been extensively studied, and their effects on the short-circuit current density (J sc ) of PSCs have been clarified. They enhance the crystallinity of the constituent materials 5,6,9,10 and thereby increase the carrier mobility, leading to higher J sc .Unfortunately, these methods are problematic. Thermal annealing can only be applied to certain polymers, and solvent annealing requires an extremely long processing time (normally several hours). 10Another proposed method is "slow drying," in which the drying time of the coated films is reduced by increasing the solvent vapor pressure of the film coating atmosphere. [12][13][14][15] This method also effectively increases the J sc of PSCs. While this method resembles solvent annealing, it has a much shorter treatment time (10−20 min). Therefore, from the viewpoint of mass-manufacturing, slow drying has...

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“…One interesting tool is the Hansen solubility parameters (HSP) analysis, which has been demonstrated to provide relevant insights into different key aspects in OPVs such as the morphology of the bulk heterojunction layer, [ 17 ] fi nding suitable additives, [ 18 ] or new formulations that may enable to replace halogenated solvents. [ 4,[6][7][8] We have recently shown for a polymer:fullerene system that alternative green solvents can be identifi ed by determining in the fi rst place the solubility parameters for the materials under investigation and, in a second step, comparing the solubility parameters for the donor and acceptor materials with tabulated data for different solvents. [ 4 ] It would be particularly interesting to generalize our fi ndings to other materials systems in order to advance a simple general rationale for the identifi cation of green solvents and, in particular, those compatible with small molecule based OPV.…”

Section: Determination Of Hsp Of N(ph-2t-dcn-et) 3 and Pc 70 Bm Usimentioning

confidence: 99%

“…Recently, several groups have studied the impact of the molecular solubility on the performance of both polymer [ 4,[14][15][16] and small molecule [ 7 ] solution-processed solar cells. This growing interest in solubility has lead to the search of suitable tools for its study.…”

Section: Determination Of Hsp Of N(ph-2t-dcn-et) 3 and Pc 70 Bm Usimentioning

confidence: 99%

Solubility Based Identification of Green Solvents for Small Molecule Organic Solar Cells

Burgués‐Ceballos

Machui

Min

et al. 2013

Adv Funct Materials

139

116

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Replacing halogenated solvents in the processing of organic solar cells by green solvents is a required step before the commercialization of this technology. With this purpose, some attempts have been made, although a general method is yet to be developed. Here, the potential of the Hansen solubility parameters (HSP) analysis for the design of green ink formulations for solution‐processed active layer in bulk heterojunction photovoltaic devices based on small molecules is demonstrated. The motivation of moving towards organic small molecules stems from their lower molecular weight and more definite structure which makes them more likely to be dissolved in a wider variety of organic solvents. In the first step, the HSP of selected active materials are determined, namely, the star‐shaped D‐π‐A tris{4‐[5′′‐(1,1‐dicyanobut‐1‐en‐2‐yl)‐2,2′‐bithiophen‐5‐yl]phenyl}amine N(Ph‐2T‐DCN‐Et)3 small molecule and fullerene derivative [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM). Secondly, computer simulations based on HSP allow the prediction of suitable green solvents for this specific material system. The most promising green solvents, according to the simulations, are then used to fabricate solar cell devices using pristine solvents and two solvents mixtures. These devices show power conversion efficiencies around 3.6%, which are comparable to those obtained with halogenated solvents. This good performance is a result of the sufficient solubility achieved after a successful prediction of good (green) solvents.

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A Systematic Approach to Solvent Selection Based on Cohesive Energy Densities in a Molecular Bulk Heterojunction System

Cited by 176 publications

References 35 publications

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells

Effect of Drying Time on Morphology and Photovoltaic Characteristics of Polymer Solar Cells of Bis-PCBM/P3HT Composites

Solubility Based Identification of Green Solvents for Small Molecule Organic Solar Cells

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A Systematic Approach to Solvent Selection Based on Cohesive Energy Densities in a Molecular Bulk Heterojunction System

Cited by 176 publications

References 35 publications

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, Jsc, and FF in Polymer:Fullerene Solar Cells

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, Jsc, and FF in Polymer:Fullerene Solar Cells

Effect of Drying Time on Morphology and Photovoltaic Characteristics of Polymer Solar Cells of Bis-PCBM/P3HT Composites

Solubility Based Identification of Green Solvents for Small Molecule Organic Solar Cells

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Product

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Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells

Quantification of Nano‐ and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J_sc, and FF in Polymer:Fullerene Solar Cells