Classification of Additives for Organic Photovoltaic Devices

Machui, Florian; Maisch, Philipp; Burgués‐Ceballos, Ignasi; Langner, Stefan; Krantz, Johannes; Ameri, Tayebeh; Brabec, Christoph J.

doi:10.1002/cphc.201402734

Cited by 49 publications

(47 citation statements)

References 31 publications

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“…Our studies do not give insight into the material specification a solvent has to fulfill for an effective SVA. Previously, we have categorized additives and found that only two solvent specific parameters are essential for casting, namely the selective solubility of a solvent for one of the semiconductors and the solvent vapor pressure at the drying temperature . It seems plausible that similar material criteria are relevant for SVA, however, this needs to be carefully studied.…”

Section: Resultsmentioning

confidence: 99%

Time‐Dependent Morphology Evolution of Solution‐Processed Small Molecule Solar Cells during Solvent Vapor Annealing

Min

Jiao

Ata

et al. 2016

Advanced Energy Materials

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103

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IntroductionSmall molecule organic solar cells (SMOSCs) have attracted extensive attention due to their well-defi ned molecular structures, high reproducibility, easy purifi cation as well as low Morphological modifi cation using solvent vapor annealing (SVA) provides a simple and widely used fabrication option for improving the power conversion effi ciencies of solution-processed bulk heterojunction (BHJ) small molecule solar cells. Previous reports on SVA have shown that this strategy infl uences the degree of donor/acceptor phase separation and also improves molecular donor ordering. A blend composed of a dithienopyrrole containing oligothiophene as donor (named UU07) and [6,6]-phenyl-C61-butyric acid methyl ester as acceptor is investigated with respect to SVA treatment to explore the dynamics of the BHJ evolution as a function of annealing time. A systematic study of the time dependence of morphology evolution clarifi es the fundamental mechanisms behind SVA and builds the structureproperty relation to the related device performance. The following two-stage mechanism is identifi ed: Initially, as SVA time increases, donor crystallinity is improved, along with enhanced domain purity resulting in improved charge transport properties and reduced recombination losses. However, further extending SVA time results in domains that are too large and a few large donor crystallites, depleting donor component in the mixed domain. Moreover, the larger domain microstructure suffers from enhanced recombination and overall lower bulk mobility. This not only reveals the importance of precisely controlling SVA time on gaining morphological control, but also provides a path toward rational optimization of device performance.

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Section: Resultsmentioning

confidence: 99%

Time‐Dependent Morphology Evolution of Solution‐Processed Small Molecule Solar Cells during Solvent Vapor Annealing

Min

Jiao

Ata

et al. 2016

Advanced Energy Materials

Self Cite

103

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“…Machui et al expanded the criteria proposed by Lee et al into a four category classification system based on a matrix of selective solubility of the donor (or acceptor) and the evaporation kinetics due to the vapor pressure of the additive . The researchers tested the effect of potential additives from each category (as shown in Figure ) on the performance of P3HT:PC 61 BM blend films, processed with up to 30% v/v of additive in CB.…”

Section: A Brief History Of Solvent Additives In Organic Photovoltaicsmentioning

confidence: 99%

Solvent Additives: Key Morphology‐Directing Agents for Solution‐Processed Organic Solar Cells

et al. 2018

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Organic photovoltaics (OPV) have the advantage of possible fabrication by energy-efficient and cost-effective deposition methods, such as solution processing. Solvent additives can provide fine control of the active layer morphology of OPVs by influencing film formation during solution processing. As such, solvent additives form a versatile method of experimental control for improving organic solar cell device performance. This review provides a brief history of solution-processed bulk heterojunction OPVs and the advent of solvent additives, putting them into context with other methods available for morphology control. It presents the current understanding of how solvent additives impact various mechanisms of phase separation, enabled by recent advances in in situ morphology characterization. Indeed, understanding solvent additives' effects on film formation has allowed them to be applied and combined effectively and synergistically to boost OPV performance. Their success as a morphology control strategy has also prompted the use of solvent additives in related organic semiconductor technologies. Finally, the role of solvent additives in the development of next-generation OPV active layers is discussed. Despite concerns over their environmental toxicity and role in device instability, solvent additives remain relevant morphological directing agents as research interests evolve toward nonfullerene acceptors, ternary blends, and environmentally sustainable solvents.

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“…We will show here that this is not a good assumption. Some solutions are intrinsically unstable or can be triggered extrinsically to aggregate [30,31]. We posit that the aging of solutions can contribute to inconsistent results published in different groups [32] and even within the same group and even when the same sample preparation procedures and experimental conditions are precisely controlled.…”

Section: Introductionmentioning

confidence: 97%

Solution aging and degradation of a transparent conducting polymer dispersion

Jacobs

Friedrich

et al. 2016

Organic Electronics

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a b s t r a c tAs organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edge X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. We expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.

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Classification of Additives for Organic Photovoltaic Devices

Cited by 49 publications

References 31 publications

Time‐Dependent Morphology Evolution of Solution‐Processed Small Molecule Solar Cells during Solvent Vapor Annealing

Time‐Dependent Morphology Evolution of Solution‐Processed Small Molecule Solar Cells during Solvent Vapor Annealing

Solvent Additives: Key Morphology‐Directing Agents for Solution‐Processed Organic Solar Cells

Solution aging and degradation of a transparent conducting polymer dispersion

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