Improved Performance of Molecular Bulk‐Heterojunction Photovoltaic Cells through Predictable Selection of Solvent Additives

Graham, Kenneth R.; Wieruszewski, Patrick M.; Stalder, Romain; Hartel, Michael J.; Mei, Jianguo; So, Franky; Reynolds, John R.

doi:10.1002/adfm.201102456

Cited by 153 publications

(131 citation statements)

References 67 publications

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“…Recently, solubility parameters of processing solvents, small molecule additives, and active material components have been used to investigate their effects on BHJ morphology. [27][28][29] HSP values are listed in Table 1 for the solvents used in our study. δ D , δ P , and δ H for PC 71 BM are recently reported to be approximately 20.2, 5.4, and 4.5 MPa 1/2 , respectively.…”

Section: Full Papermentioning

confidence: 99%

Solvent‐Polarity‐Induced Active Layer Morphology Control in Crystalline Diketopyrrolopyrrole‐Based Low Band Gap Polymer Photovoltaics

Ferdous

Liu

Wang

et al. 2013

Advanced Energy Materials

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Solvent effects on the morphology of diketopyrrolopyrrole (DPP)‐based low band gap polymer (PDPPBT):phenyl‐C71‐butyric acid methyl ester (PC71BM) blends are studied systematically using a mixture of a non‐aromatic polar primary solvent with high boiling point (b.p.) secondary solvents of increasing polarities. An unfavorable solvent‐PC71BM interaction, due to a polarity mismatch, leads to significantly different morphology, also affecting the growth process of polymer crystallites. Non‐aromatic polar solvent produces large PC71BM aggregates that increase in size with the addition of non‐polar secondary solvents. The size scales of the aggregates decrease markedly when polar solvents are instead used as the secondary solvents. This processing method fundamentally changes the behavior of phase separation, creating a percolated fibrillar type network structure. Moreover, polar secondary solvents with lower vapor pressures reduce the interfibrillar distances that enhance the device performance even more. Power conversion efficiencies (PCE) of 0.03% to 5% are obtained, depending on the solvent system used.

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Section: Full Papermentioning

confidence: 99%

Solvent‐Polarity‐Induced Active Layer Morphology Control in Crystalline Diketopyrrolopyrrole‐Based Low Band Gap Polymer Photovoltaics

Ferdous

Liu

Wang

et al. 2013

Advanced Energy Materials

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“…Although these materials do not really coassemble but rather phase separate, both molecular components have mutual interactions and their concomitant aggregation processes compete for available space (31). Perhaps for this reason, manipulating the aggregation pathways by adding cosolvents such as 1,8-diiodooctane has a strong effect on the resulting morphology of organic devices (32)(33)(34).…”

Section: Discussionmentioning

confidence: 99%

Model-driven optimization of multicomponent self-assembly processes

Korevaar

Grenier

Markvoort

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Here, we report an engineering approach toward multicomponent self-assembly processes by developing a methodology to circumvent spurious, metastable assemblies. The formation of metastable aggregates often hampers self-assembly of molecular building blocks into the desired nanostructures. Strategies are explored to master the pathway complexity and avoid off-pathway aggregates by optimizing the rate of assembly along the correct pathway. We study as a model system the coassembly of two monomers, the R-and S-chiral enantiomers of a π-conjugated oligo(p-phenylene vinylene) derivative. Coassembly kinetics are analyzed by developing a kinetic model, which reveals the initial assembly of metastable structures buffering free monomers and thereby slows the formation of thermodynamically stable assemblies. These metastable assemblies exert greater influence on the thermodynamically favored self-assembly pathway if the ratio between both monomers approaches 1:1, in agreement with experimental results. Moreover, competition by metastable assemblies is highly temperature dependent and hampers the assembly of equilibrium nanostructures most effectively at intermediate temperatures. We demonstrate that the rate of the assembly process may be optimized by tuning the cooling rate. Finally, it is shown by simulation that increasing the driving force for assembly stepwise by changing the solvent composition may circumvent metastable pathways and thereby force the assembly process directly into the correct pathway.kinetic modeling | chiral amplification | supramolecular polymers | systems chemistry | pathway selection S elf-assembled nanostructures often are considered to be in fast exchange with their molecular building blocks (1). Although this is true for highly dynamic systems, the assembly of more rigid systems-i.e., systems most often used in applicationshave relatively slow dynamics and are often not in equilibrium (2-5). The long lifetime of the resulting assemblies allows the hierarchical construction of functional nanostructures from selfassembly of multiple components, because aggregates formed in earlier steps will not reequilibrate after addition of subsequent components. Via this approach, 1D multisegment nanorods (6) have been assembled, as have supramolecular electronic structures containing different types of wires (7) and p-n junctions (8). Slow self-assembly dynamics also play a critical role in the processing of organic materials such as bulk heterojunction solar cells. For example, prolonged annealing often is required to obtain optimal morphologies of electron donor and acceptor components (9-11). A drawback of the slow monomer exchange dynamics, however, is that the molecular components may get trapped easily in metastable off-pathway assemblies that hamper assembly along the correct pathway, a phenomenon known as pathway complexity (12). Hence, obtaining the desired supramolecular morphology often is nontrivial, and many variables, including solvent composition, concentration, temperature, and preparation ...

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“…After annealing at 100°C, solar cells made from 2l showed a PCE of up to 1.76 %, with a V OC of 0.74 V, J SC of 6.3 mA cm −2 , and fill factor of 0.38 [35]. By combining solvent additives with complementary effects, further refinement of the device processing conditions was achieved, and the PCE of 2l was further increased to near 3.7 % [36].…”

Section: Dyesmentioning

confidence: 99%

Organic Semiconductor Photovoltaic Materials

Zhang

2015

Lecture Notes in Chemistry

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Organic solar cells (OSCs) are an emerging alternative photovoltaic technology and thus they have recently gained much attention. In this chapter, recent developments in organic photovoltaic materials, involving small molecule donors and non-fullerene acceptors for vacuum and solution-processed photovoltaic cells, are summarized. A general overview of the structure-property relationships of these organic photovoltaic materials and the design rules for such materials is presented. Critical factors which determined their photophysical properties such as energy levels, absorption, and carrier mobilities are also highlighted.

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Improved Performance of Molecular Bulk‐Heterojunction Photovoltaic Cells through Predictable Selection of Solvent Additives

Cited by 153 publications

References 67 publications

Solvent‐Polarity‐Induced Active Layer Morphology Control in Crystalline Diketopyrrolopyrrole‐Based Low Band Gap Polymer Photovoltaics

Solvent‐Polarity‐Induced Active Layer Morphology Control in Crystalline Diketopyrrolopyrrole‐Based Low Band Gap Polymer Photovoltaics

Model-driven optimization of multicomponent self-assembly processes

Organic Semiconductor Photovoltaic Materials

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