Real-time evaluation of thin film drying kinetics using an advanced, multi-probe optical setup

Güldal, Nusret S.; Kassar, Thaer; Berlinghof, Marvin; Ameri, Tayebeh; Osvet, Andres; Pacios, Roberto; Destri, Giovanni Li; Unruh, Tobias; Brabec, Christoph J.

doi:10.1039/c5tc03448e

Cited by 33 publications

(51 citation statements)

References 40 publications

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“…36,38 The LS signal of the additive-free sample (Fig. 7b) showed a sharp increase right before drying and stabilized quickly with the completion of drying.…”

Section: In Situ Characterizationsmentioning

confidence: 99%

“…38 We were able to attain a complete picture on the interplay between the thermodynamic and kinetic processes, governing the drying. In particular from in situ PL measurements, we concluded that the microstructure formation of additive-free DPP-TT-T : PCBM was dominated by the solubility limit of the polymer in o-xylene which caused a solid-liquid phase separation-induced gelation, hindering the crystal growth.…”

Section: In Situ Characterizationsmentioning

confidence: 99%

“…38 In this manuscript, we extend the study on DPP-TT-T : PCBM by utilizing DIO as a better solvent for both components than the host solvents in order to visualize the precise function of an additive in an ink formulation and to describe an alternative morphology formation mechanism for polymer : fullerene bulk-heterojunctions. For that matter, we use our in situ characterization setup to examine the drying kinetics and morphology evolution.…”

Section: 9-12mentioning

confidence: 99%

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Controlling additive behavior to reveal an alternative morphology formation mechanism in polymer : fullerene bulk-heterojunctions

et al. 2016

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aOne of the most employed morphology optimization methods to design better performing organic photovoltaic devices is ink formulation engineering with additives. In this work, by employing a suboptimal host solvent mixture and 1,8-diiodooctane (DIO) as a very optimal solvent for both components in poly-thieno [3,2b]thiophene-diketopyrrolopyrrole-co-thiophene (DPP-TT-T)-based bulkheterojunctions (BHJ), an alternative, previously unknown mechanism of additive behavior on BHJ microstructure formation is presented. In situ characterization methods involving grazing incidence X-ray diffraction, white-light reflectometry, laser light scattering and photoluminescence during film drying reveal that the microstructure formation under the influence of DIO is led towards thermodynamic equilibrium during host solvent drying, and the kinetics of morphology formation (i.e. polymer crystallization, fullerene aggregation.) are controlled dominantly by the additive during its evaporation. Ex situ X-ray-based characterization methods, such as scanning transmission X-ray microspectroscopy (STXM) and resonant soft X-ray scattering (R-SoXS), additionally reveal that the microstructure of dried films favors smaller domain sizes with purer domains, smaller fullerene aggregates, bimodal polymer crystallization relative to the substrate and more face-on molecular orientation relative to the donor/acceptor interface, which at the end lead to better performing devices with power conversion efficiencies ranging from 1.25% to 4.68%.

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“…36,38 The LS signal of the additive-free sample (Fig. 7b) showed a sharp increase right before drying and stabilized quickly with the completion of drying.…”

Section: In Situ Characterizationsmentioning

confidence: 99%

Section: In Situ Characterizationsmentioning

confidence: 99%

Section: 9-12mentioning

confidence: 99%

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Controlling additive behavior to reveal an alternative morphology formation mechanism in polymer : fullerene bulk-heterojunctions

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“…The importance of the drying pathway has been recognised by several authors and has been found to considerably impact performances. [22][23][24]…”

Section: Annealing Protocolsmentioning

confidence: 99%

Impact of solution phase behaviour and external fields on thin film morphology: PCBM and RRa-P3HT model system

Guilbert

Cabral

2017

Soft Matter

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We report the impact of the ternary solution phase behaviour on the film morphology and crystallization of a model polymer:fulerene system. We employ UV-Vis absorption spectroscopy, combined with sequential filtration and dilution, to establish the phase diagram for regio-random poly(3-hexylthiophene-2,5-diyl) and phenyl-C61-butyric acid methyl ester (PCBM) in chlorobenzene. The low polymer regio-regularity enables us to focus solely on PCBM crystallization. Films are systematically cast from one-and two-phase regions, with various polymer:fullerene ratios and concentrations in solution establishing a clear link between homogeneous and heterogenous nucleation, and the role of pre-formed aggregates from solutions. Increasing annealing temperature reveals a highly non-otonic nucleation profile, while the crystal growth rate increases steadilly within the range investigated, from 120-200°C. A maximum nucleation rate is observed at 170°C, all but vanishing at 200°C, well below the neat melting point of PCBM. UV ozonolysis is employed to vary substrate energy, and is shown to have a profound impact on crystallization, increasing nucleation rate and promoting a binary crystallization process. Exposure to light, under inert atmosphere, on the other hand, effectively suppresses homogeneous nucleation, but has a considerably smaller effect on heterogeneous nucleation, either from solution aggregates or substrate-driven.Our results establish a quantitative link between solution thermodynamics, crystallization and provide insight into morphological design based on process parameters in a proxy organic photovoltaic system. Journal Name ARTICLEThis journal is

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“…14,15,[18][19][20][21][22][23] Recent processing approaches, however, have not always been able to overcome the complexity of separating intrinsic from extrinsic effects.…”

Section: 13mentioning

confidence: 99%

High performance all-small-molecule solar cells: engineering the nanomorphology via processing additives

et al. 2016

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adThe use of small volumes of solvent additives (SAs) or little amounts of non-volatile additives is a processing approach that has been implemented in many high/record performing bulk heterojunction (BHJ) organic solar cells (OSCs). Here, the effects of six SA systems and a molecular additive di-2-thienyl-2,1,3-benzothiadiazole (DTBT) were studied with respect to the photovoltaic parameters of solutionprocessed all small molecule solar cells (all-SMSCs) based on the BDTT-S-TR:NIDCS-MO system. An effective strategy with binary additives has been employed in this all-SM system, where a small amount, 0.75 vol% 1,8-diiodooctane (DIO) and 2 wt% DTBT were added to the casting solution. This efficient SA approach yielded the highest power conversion efficiency (PCE) of 5.33%. The relevant additives facilitate phase separation in the nm domains and improve bulk transport as evidenced by photoluminescence (PL), atomic force microscopy (AFM), X-ray diffraction (XRD) and space charge limited current (SCLC) measurements.

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Real-time evaluation of thin film drying kinetics using an advanced, multi-probe optical setup

Cited by 33 publications

References 40 publications

Controlling additive behavior to reveal an alternative morphology formation mechanism in polymer : fullerene bulk-heterojunctions

Controlling additive behavior to reveal an alternative morphology formation mechanism in polymer : fullerene bulk-heterojunctions

Impact of solution phase behaviour and external fields on thin film morphology: PCBM and RRa-P3HT model system

High performance all-small-molecule solar cells: engineering the nanomorphology via processing additives

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