Correlating Stiffness, Ductility, and Morphology of Polymer:Fullerene Films for Solar Cell Applications

Awartani, Omar; Lemanski, Bethany I.; Ro, Hyun Wook; Richter, Lee J.; DeLongchamp, Dean M.; O’Connor, Brendan

doi:10.1002/aenm.201200595

Cited by 132 publications

(235 citation statements)

References 51 publications

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“…The tensile modulus of 287 ± 19 MPa for RR-98 film was in good agreement with previously reported values for P3HT films, i.e., 250 ± 60 MPa 38 and 220 ± 30 MPa. 39 The tensile modulus gradually decreased from 287 MPa for RR-98 to 13 MPa for RR-64. The tensile modulus (13 MPa) for RR-64 was especially low, even lower than the tensile modulus values reported to date for other conjugated polymer films.…”

Section: Macromoleculesmentioning

confidence: 98%

Tuning Mechanical and Optoelectrical Properties of Poly(3-hexylthiophene) through Systematic Regioregularity Control

Kim¹,

Kim²,

Lee³

et al. 2015

Macromolecules

203

244

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While the regioregularity (RR) of conjugated polymers is known to have a strong influence on their inherent properties, systematic study of the RR effect has been limited due to the lack of a synthetic methodology. Herein, we successfully produced a series of poly(3-hexylthiophene)s (P3HTs) having a wide range of RR from 64 to 98%. Incorporation of controlled amounts of head-to-head (H−H) coupled dimer in modified Grignard metathesis polymerization allows a facile tuning of the RR of the P3HTs with comparable molecular weight and low polydispersity. Then, we investigated the effect of RR on structural, electrical, and mechanical properties of P3HTs in which a higher content of H−H regio-defects, namely lower RR, systematically lowered the degree of crystallinity. Although high RR P3HT (98%) had higher charge carrier mobility (1.81 × 10 −1 cm 2 V −1 s −1 ), its strong crystallinity induced high brittleness and stiffness, resulting in device failure under a very small strain, as shown in tensile and bending tests. The tensile modulus was reduced significantly from 287 MPa (RR 98%) to 13 MPa (RR 64%), and also the RR 64% P3HT film had much better mechanical resilience with an order of magnitude higher elongation at break than that of the RR 98% polymer. Our findings suggest that the mechanical and electrical properties of conjugated polymers can be systematically tuned by controlling the RR to meet the purposes of various organic electronic applications, i.e., flexible portable devices vs high-performance panels.

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Section: Macromoleculesmentioning

confidence: 98%

Tuning Mechanical and Optoelectrical Properties of Poly(3-hexylthiophene) through Systematic Regioregularity Control

Kim¹,

Kim²,

Lee³

et al. 2015

Macromolecules

203

244

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“…The current OPV literature remains predominantly concerned with the design of new molecules and polymers with well-defined electronic, optical, and redox properties as well as investigations of the intrinsic electronic processes underlying photocurrent generation. Although there is increasing interest in the mechanical properties of BHJ active layers, [1][2][3][4][5][6][7][8][9] and such studies are common for traditional polymers, [10][11] the efforts in the OPV arena remain limited when compared to performance efficiency studies. [12][13][14][15][16] Along with the electronic processes involved in photocurrent generation, the active-layer mechanical properties inherently depend on the multiphase morphology of the BHJ thin films [17][18][19][20][21][22] and therefore are contingent on the thin-film processing protocols and the nature and strength of non-covalent, solid-state intermolecular interactions.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is not clear 4 how the chemical substitution patterns of the solubilizing groups influence the electronic and mechanical properties of these composite materials, as there remain many intricate details that need to be unfurled at the molecular-and nano-scales. Notably, fullerenes have been exploited in other composite blends, [27][28][29][30][31][32] however their traction in these applications remains limited due to restrictions in terms of solubility, processability, and the resulting materials properties.…”

Section: Introductionmentioning

confidence: 99%

Molecular-Scale Understanding of Cohesion and Fracture in P3HT:Fullerene Blends

Tummala

Bruner

Risko

et al. 2015

ACS Appl. Mater. Interfaces

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Abstract.Quantifying cohesion and understanding fracture phenomena in thin-film electronic devices are necessary for improved materials design and processing criteria. For organic photovoltaics (OPVs), the cohesion of the photoactive layer portends its mechanical flexibility, reliability, and lifetime. Here, the molecular mechanism for the initiation of cohesive failure in bulk heterojunction (BHJ) OPV active layers derived from the semiconducting polymer poly-(3-hexylthiophene) [P3HT] and two mono-substituted fullerenes is examined experimentally and through molecular-dynamics simulations. The results detail how, under identical conditions, cohesion significantly changes due to minor variations in the fullerene adduct functionality, an important materials consideration that needs to be taken into account across fields where soluble fullerene derivatives are used.

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“…16 The composite stack is immersed in a deionized (DI) water bath where the PEDOT:PSS layer dissolves and the donor substrate detaches from the film. 17 The P3HT:PCBM film, which is now adhered to the PDMS slab, was removed from the DI water and dried with N 2 gas. The composite was then strained and printed onto a receiving substrate that consists of spun cast PEDOT:PSS film on an indium tin oxide (ITO) coated glass substrate.…”

mentioning

confidence: 99%

Organic photovoltaic cells with controlled polarization sensitivity

Awartani

Kudenov

O’Connor

2014

Applied Physics Letters

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In this study, we demonstrate linearly polarized organic photovoltaic cells with a well-controlled level of polarization sensitivity. The polarized devices were created through the application of a large uniaxial strain to the bulk heterojunction poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) film and printing the plastically deformed active layer onto a PEDOT:PSS and indium tin oxide coated glass substrate. The P3HT:PCBM layer is processed such that it is able to accommodate high strains (over 100%) without fracture. After printing the strained films, thermal annealing is used to optimize solar cell performance while maintaining polarization sensitivity. A dichroic ratio and short circuit current ratio of %6.1 and %1.6 were achieved, respectively. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4868041] Organic photovoltaics (OPVs) have attracted significant research interest due to several advantageous characteristics, including low-cost processing onto flexible substrates, tunable properties through material synthesis, and their use of earth abundant materials. 1 A unique characteristic of polymer semiconductors is that they commonly have an optical transition dipole moment (p À p*) that is aligned along the polymer backbone. 2,3 Thus, aligning the polymer backbone uniaxially in the plane of the film results in anisotropic optoelectronic properties. 4-6 Aligning polymer semiconductors has been exploited to study charge transport in organic field effect transistors (OFETs) 4,7 and for polarized electroluminescence in organic light emitting diodes. 8 Alignment also provides an opportunity to develop polarization sensitive OPV devices. 6,9 Polarization sensitive photovoltaic cells may be beneficial for a number of applications including polarized light detectors (e.g., remote detection), 10 and power generation (e.g., polarized light harvesting in LCD displays). 6 In addition, alignment of the polymer chains in an OPV cell may provide insight into energy conversion processes. 11 There have been a number of techniques used to uniaxially align conjugated polymer films that have focused on alignment of homogeneous polymer systems. 4,7,[12][13][14] In polymer:fullerene blends, such as poly(3-hexylthiophene): Phenyl-C61-butyric acid methyl ester (P3HT:PCBM), alignment of the P3HT component has recently been demonstrated by (1) mechanically rubbing the film at an elevated temperature (150 C) 6 and (2) through directed crystallization. 15 While the directed crystallization approach was successful, it required processing with a crystallizing solvent 1,3,5-trichlorobenzene (TCB) and OPV devices using this approach have yet to be produced. 15 Furthermore, while the mechanical rubbing approach effectively aligns P3HT in P3HT:PCBM blend films, the physically interrogating rubbing process at an elevated temperature may be detrimental to the film's quality. Additionally, the ability to control the degree of alignment with this approach is unclear. In this study, we demonstrate a facile approa...

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Correlating Stiffness, Ductility, and Morphology of Polymer:Fullerene Films for Solar Cell Applications

Cited by 132 publications

References 51 publications

Tuning Mechanical and Optoelectrical Properties of Poly(3-hexylthiophene) through Systematic Regioregularity Control

Tuning Mechanical and Optoelectrical Properties of Poly(3-hexylthiophene) through Systematic Regioregularity Control

Molecular-Scale Understanding of Cohesion and Fracture in P3HT:Fullerene Blends

Organic photovoltaic cells with controlled polarization sensitivity

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