Complementary solvent additives tune the orientation of polymer lamellae, reduce the sizes of aggregated fullerene domains, and enhance the performance of bulk heterojunction solar cells

Liu, Chih-Ming; Su, Yi‐Cheng; Jiang, Jian-Ming; Chen, Hsiu-Cheng; Lin, Shu-Wei; Su, Chun‐Jen; Jeng, U‐Ser; Wei, Kung‐Hwa

doi:10.1039/c4ta04804k

Cited by 75 publications

(51 citation statements)

References 69 publications

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“…We observe here that face-on orientation as shown, for example, by the intensity of π−π stacking peak 010 is more pronounced for the blend film with DIO. Similar findings were reported in [48], supporting the idea that DIO is beneficial to the crystallinity of PCE11 chains in blends, resulting in better charge transport. The ordering of the donor polymer is a very important parameter affecting the charge transport and interconnectivity within the blends, thus improving the solar cell performance [47].…”

Section: Structural Properties Before Stretchingsupporting

confidence: 87%

Section: Structural Properties Before Stretchingsupporting

confidence: 87%

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Direct Observations of the Structural Properties of Semiconducting Polymer: Fullerene Blends under Tensile Stretching

et al. 2020

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We describe the impact of tensile strains on the structural properties of thin films composed of PffBT4T-2OD π-conjugated polymer and PC71BM fullerenes coated on a stretchable substrate, based on a novel approach using in situ studies of flexible organic thin films. In situ grazing incidence X-ray diffraction (GIXD) measurements were carried out to probe the ordering of polymers and to measure the strain of the polymer chains under uniaxial tensile tests. A maximum 10% tensile stretching was applied (i.e., beyond the relaxation threshold). Interestingly we found different behaviors upon stretching the polymer: fullerene blends with the modified polymer; fullerene blends with the 1,8-Diiodooctane (DIO) additive. Overall, the strain in the system was almost twice as low in the presence of additive. The inclusion of additive was found to help in stabilizing the system and, in particular, the π–π packing of the donor polymer chains.

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Section: Structural Properties Before Stretchingsupporting

confidence: 87%

Section: Structural Properties Before Stretchingsupporting

confidence: 87%

Direct Observations of the Structural Properties of Semiconducting Polymer: Fullerene Blends under Tensile Stretching

et al. 2020

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“…Developments of GISAXS/GIWAXS patterns could be observed simultaneously a few seconds after starting the spin‐coating process. The scattering intensity along the in‐plane scattering wavevector q y in the GISAXS patterns (Figure b) increased with time, revealing mainly the characteristic PCBM aggregation behavior, as demonstrated previously . Closely followed (Figure c) was the growth of the characteristic (100) reflection of P3HT crystallites centered at q z = 0.381 Å −1 (corresponding to a lamellar spacing d 100 = 16.5 Å) in the q z direction of the GIWAXS patterns, revealing highly oriented and short‐range ordered domains with an edge‐on structure (i.e., the polymer molecular plane is normal to the film surface) .…”

Section: Resultssupporting

confidence: 54%

Surface Layering and Supersaturation for Top‐Down Nanostructural Development during Spin Coating of Polymer/Fullerene Thin Films

Chuang

et al. 2017

Advanced Energy Materials

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This study provides new evidence on a long postulated mechanism of phase separation in a polymer/fullerene mixture during spin coating for controlled nanodomains of oriented crystallization and heterojunctions that favor applications in polymer solar cells (PSCs). The simultaneous nanoscale phase separation and crystallization during spin coating of the mixture are traced using in situ grazing‐incidence small‐ and wide‐angle X‐ray scattering. Combined with the complimentary results from time‐resolved optical reflectance spectroscopy, transient stratification of the liquid film during the transition from the flow‐ to evaporation‐dominated stage of spin coating is disclosed; the vertical liquid–liquid phase separation incubates a supersaturated skin layer where fullerene aggregation and polymer crystallization occur and develop concomitantly. Shortly after the transition, the near‐surface structural development is largely pinned, leaving the solvent‐rich bottom layer to diminish via solvent diffusion and evaporation through the thickened skin layer that finally condenses into the spin‐coated film upon solvent depletion. The shear‐enhanced surface layering and supersaturation for the surface‐down nanostructural development are unexpected in all the existing structural models for PSCs. The mechanistic understanding of coupled vertical phase separation and local nanosegregation provides new insights and alternative strategy to the morphology control of spin‐cast PSC active layers in particular and various solution‐processed polymeric films in general.

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“…Optoelectronic devices, such as photovoltaic sensors, solar cells, and organic light-emitting diodes (OLEDs), that are based on a donor/acceptor binary hybrid of conjugated polymers have attracted the attention of many researchers because they are inexpensive, lightweight, and easy to prepare. Additionally, they exhibit high mechanical flexibility and are an ecofriendly energy source [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Triplet Energy Transfer Mechanism of Ternary Organic Hybrid Thin Films of PFO/MEH-PPV/CsPbBr3 Perovskite Quantum Dots

et al. 2020

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The triplet energy transfer mechanism of novel poly(9,9-di-n-octylflourenyl-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/CsPbBr3 perovskite quantum dot (PQD) hybrid thin films was comprehensively investigated. The concentrations of PFO and MEH-PPV in all the specimens were fixed, while the PQD content was varied with various weight ratios and premixed by a solution blending method before it was spin-coated onto glass substrates. The triplet non-radiative Förster resonance energy transfers (FRETs) in the PFO/MEH-PPV/PQDs ternary blend, the dual FRET from PFO to both PQDs and MEH-PPV, and the secondary FRET from PQDs to MEH-PPV were observed. The values of the Förster radius (Ro) of FRET from PFO to MEH-PPV in the presence of various PQD contents (Case I) increased from 92.3 to 104.7 Å, and they decreased gradually from 68.0 to 39.5 Å for FRET from PFO to PQDs in the presence of MEH-PPV (Case II). These Ro values in both cases confirmed the dominance of FRET in ternary hybrid thin films. Upon increasing the PQD content, the distance between the donor and acceptor molecules (RDA) and the conjugation length (Aπ) in both cases gradually decreased. The small values of Ro, RDA, and Aπ with a decrease in the energy transfer lifetime (τET) due to an increase in the PQD contents in both Cases I and II confirmed the efficient FRET in the hybrid. To prevent intermolecular transfer in PFO, the concentrations of MEH-PPV (Case I) and PQDs (Case II) should be decreased to a range of 0.57–0.39 mM and increased in the range of 1.42–7.25 mM.

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Complementary solvent additives tune the orientation of polymer lamellae, reduce the sizes of aggregated fullerene domains, and enhance the performance of bulk heterojunction solar cells

Abstract: The binary additives approach lead to a better active layer that combines the face-on polymer lamellae and finer fullerenes dispersion.

Cited by 75 publications

References 69 publications

Direct Observations of the Structural Properties of Semiconducting Polymer: Fullerene Blends under Tensile Stretching

Direct Observations of the Structural Properties of Semiconducting Polymer: Fullerene Blends under Tensile Stretching

Surface Layering and Supersaturation for Top‐Down Nanostructural Development during Spin Coating of Polymer/Fullerene Thin Films

Triplet Energy Transfer Mechanism of Ternary Organic Hybrid Thin Films of PFO/MEH-PPV/CsPbBr3 Perovskite Quantum Dots

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