Conjugated Block Copolymer Photovoltaics with near 3% Efficiency through Microphase Separation

Guo, Changhe; Lin, Yan‐Ru; Witman, Matthew; Smith, Kendall A.; Wang, Cheng; Hexemer, Alexander; Strzalka, Joseph; Gomez, Enrique D.; Verduzco, Rafael

doi:10.1021/nl401420s

Cited by 259 publications

(314 citation statements)

References 66 publications

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“…The highest performing example of this strategy to date achieved a power conversion efficiency of 3.1% employing poly(3-hexylthiophene) (P3HT) as the donor material and poly(2,7-(9′,9′-dioctylfluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PFTBT) as the acceptor material in the BCP P3HT-b-PFTBT (Figure 2a, R = H). 13 The authors observed phase separation into 9 nm domains in this system, which may have contributed to the high performance. However, in a subsequent investigation of 30 closely related P3HT-b-PFTBT BCP derivatives, little or no phase separation was obtained regardless of processing conditions.…”

Section: Introductionmentioning

confidence: 79%

“…However, in these blended materials, the choice of solvent is restricted to those that can accommodate both components to some threshold level. To date, this most often dictates the use of chlorinated and toxic solvents that are disadvantageous for industrial applications, 13 although there have been recent advances in the use of non-chlorinated aromatic solvents such as mesitylene and anisole. 14,15 One alternative to this blending approach is the covalent linkage of donor and acceptor material into a single entity.…”

Section: Introductionmentioning

confidence: 99%

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The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Mitchell

Wong

Thelakkat

et al. 2016

Polym J

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Nanoscale domains of donor and acceptor materials are crucial for charge generation in organic photovoltaic devices. These domains are difficult to achieve reproducibly in blended materials, but could be engineered into single-material active layers composed of donor-acceptor block copolymers (BCPs). In this work, we report the synthesis and purification of two novel fully conjugated BCPs, P3HT-b-PF TEG TBT and P3HT-b-PF TEG T6BT. To enhance phase separation and self-assembly, these two polymers incorporate tetraethylene glycol side chains into the PFTBT acceptor block, generating an amphiphilic system. The chemical disparity of the donor and acceptor blocks allowed the development of a purification strategy capable of isolating the desired BCP from homopolymer contaminants. This is a significant improvement over previous systems in which homopolymer contaminants can dominate the reaction mixture, affecting performance and morphology. We show that preliminary morphological analysis indicates spontaneous phase separation in thin films, demonstrating the efficacy of this design strategy and the potential application of these materials in organic photovoltaic devices.

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Mitchell

Wong

Thelakkat

et al. 2016

Polym J

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“…In spite of these remarkable performances, the realization of solution-processed BHJ solar cells still poses a number of problems related to both the nature of the active materials and the fabrication process [11]. For example, the finecontrol of phase separation and achieving high chargecarrier mobility in active layers are still very difficult with BHJ solar cells [ As another interesting strategy, electron donoracceptor dyad, triad, multiad and block copolymer molecules or all-in-one molecules where the electron donor (D) and acceptor (A) units are covalently linked in a single molecule have been reported for their potential as photovoltaic materials [12,[14][15][16][17][18][19]. These single-component photovoltaic materials possess multifunctions such as light harvesting, exciton dissociation and electron and hole transport.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, several major advantages, such as a considerable simplification of device fabrication, stabilization of the morphology of the active material, and efficient (or fast) charge separation can be expected in the single-component OSCs [11]. At present, the PCE for single-component OSCs has surpassed 2% [12,15,17], which is lower than that of BHJ solar cells. This is because the design of electron donor-acceptor molecules for efficient single-component OSCs is in fact difficult.…”

Section: Introductionmentioning

confidence: 99%

Mesogenic complementary absorbing dyads based on porphyrin and perylene units

Kong

Gong

Dai

et al. 2018

J. Porphyrins Phthalocyanines

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Five novel dyads, consisting of a tetraphenylporphyrine unit connected to a perylene monoimide diester unit via a flexible bridge -CONH-(CH 2 ) n -(n = 4, 6, 8, 10 and 12), have been synthesized. Their structures were characterized by 13 C and 1 H nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry and elemental analysis. The UV-vis absorption spectra revealed these dyads have broad optical absorption in the ultraviolet and visible regions due to the complementary absorption of the two units. The differential scanning calorimetry traces and polarized optical microscopy textures showed all these dyads have columnar liquid crystal phases. Cyclic voltammetry revealed the highest occupied molecular orbitals of the dyads located on the porphyrin units, and the lowest unoccupied molecular orbitals located on the perylene units. In addition, these results were in agreement with that of the theoretical modeling. When excited at 423 or 473 nm, the photoluminescent emission spectra showed that the degree of fluorescence quenching of porphyrin units increased as the spacers became shorter. This quenching was ascribed to intramolecular photoinduced electron transfer, which also induced the dyad molecules to form the charge-separated states. The charge-separated molecules were further confirmed by the photocurrent response curves. These behaviors of broad absorption of the ultraviolet-visible light, yielding the charge-separated states of the molecules when excited and the formation of columnar liquid crystal phase made these dyads candidates for single-component photovoltaic active materials.

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“…The covalent interactions can be effectively tapped to form block copolymers (BCPs) which has numerous applications such as, an etch mask for nano/meso scale patterning, photovoltaic devices, drug delivery, etc [1][2][3][4][5][6]. Apart from the cited applications, BCPs are also being explored for their applicability as photonic materials [7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Optical and rheological studies on weak gel-sol transition in aqueous solutions of poly(N-isopropylacrylamide)-block-polystyrene

Prasath¹,

Brijitta²,

Tata³

et al. 2017

Express Polym. Lett.

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IntroductionWith the recent developments in synthesis strategies of novel macromolecules, it is now possible to tune the macromolecular size and shape by covalent and non-covalent interactions. The covalent interactions can be effectively tapped to form block copolymers (BCPs) which has numerous applications such as, an etch mask for nano/meso scale patterning, photovoltaic devices, drug delivery, etc [1][2][3][4][5][6]. Apart from the cited applications, BCPs are also being explored for their applicability as photonic materials [7][8][9][10][11][12]. Among the numerous strategies of controlled/living free-radical polymerization for the synthesis of BCPs, reversible addition-fragmentation chain transfer (RAFT) polymerization process stays in the forefront. The advantage of RAFT polymerization is that, it results in polymers with controlled molecular weight and with narrow polydispersities and offers a wide Abstract. The optical and rheological properties of aqueous solutions of block copolymer composed of low molecular weight poly(N-isopropylacrylamide)-b-polystyrene are studied as a function of temperature. From light scattering measurements the block copolymer solution is found to form micelles at very low concentrations and the critical micellar concentration is identified as 0.005 wt%. Apart from the concentration dependence, a unique temperature dependent micelle formation is noted at 34°C. Further, temperature dependent refractive index measurements shows that the refractive index increases with temperature (beyond the lower critical solution temperature, 31.6°C of the polymer), and is attributed to the stable rearrangement of the proximal hydrophobic isopropyl-polystyrene chains in the collapsed polymer so as to overcome the steric hindrance effects offered by the hydrophobic chains. In the polymer concentrations investigated for rheological studies, the solution flows, yet manifested solid like behavior with G′ > G″ with the modulus being frequency dependent and the magnitude of G′ two-fold higher than G″ implying a weak gel state. Weak gel states are in general noted at high temperatures in most of the polymer systems, contrary to this, in our studies weak gel state is observed at lower temperature. Further, a transition from weak gel to sol state is observed at slightly elevated temperatures. The reason for the existence of weak gel state below the lower critical solution temperature is due to the micellar entanglements of poly(N-isopropylacrylamide)-b-polystyrene with one another and whereas above the lower critical solution temperature disentanglement of the micelles makes the system behave like a viscoelastic liquid.

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Conjugated Block Copolymer Photovoltaics with near 3% Efficiency through Microphase Separation

Cited by 259 publications

References 66 publications

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

The synthesis and purification of amphiphilic conjugated donor–acceptor block copolymers

Mesogenic complementary absorbing dyads based on porphyrin and perylene units

Optical and rheological studies on weak gel-sol transition in aqueous solutions of poly(N-isopropylacrylamide)-block-polystyrene

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