Challenges and Opportunities in the Development of Conjugated Block Copolymers for Photovoltaics

Lee, Young-Min; Gomez, Enrique D.

doi:10.1021/acs.macromol.5b00112

Cited by 107 publications

(105 citation statements)

References 147 publications

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“…101 c. Rigid polymer hosts. As discussed earlier, a long triplet diffusion length can arise either from an extended exciton lifetime or from a larger diffusion coefficient, D. Monguzzi and co-workers increased the triplet exciton lifetime by embedding the molecular upconversion materials in a rigid polystyrene (PS) matrix that inhibits intramolecular relaxation.…”

Section: Hierarchical Order In Harvesting Triplet Excitonsmentioning

confidence: 99%

Triplet transport in thin films: fundamentals and applications

Tang

2017

Chem. Commun.

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Triplet excitons are key players in multi-excitonic processes like singlet fission and triplet-triplet annihilation based photon upconversion, which may be useful in next-generation photovoltaic devices, photocatalysis and bioimaging. Here, we present an overview of experimental and theoretical work on triplet energy transfer, with a focus on triplet transport in thin films. We start with the theory describing Dexter-mediated triplet energy transfer and the fundamental parameters controlling this process. Then we summarize current experimental methods used to measure the triplet exciton diffusion length. Finally, the use of hierarchically ordered structures to improve the triplet diffusion length is presented, before concluding with an outlook on the remaining challenges.

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Section: Hierarchical Order In Harvesting Triplet Excitonsmentioning

confidence: 99%

Triplet transport in thin films: fundamentals and applications

Tang

2017

Chem. Commun.

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“…The first system is a model for a regioregular P3HT‐PCBM junction, where exciton and charge delocalization are found to exert a pronounced effect on the ultrafast charge separation dynamics. The second system represents alternative architectures that rely on the self‐assembly of covalently bound DA block co‐polymers or co‐oligomers . We specifically address recently developed oligothiophene‐perylene diimide (OT‐PDI) based DA dyad and DAD triad combinations that are organized in smectic liquid crystalline (LC) films or else lamellar mesophases .…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

Polkehn

Eisenbrandt

Tamura

et al. 2017

Int J of Quantum Chemistry

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We review recent work employing high-dimensional quantum dynamical techniques to study ultrafast charge separation in functional organic materials, in view of understanding the key microscopic factors that lead to efficient charge generation in photovoltaics applications. As highlighted by recent experiments, these processes can be guided by quantum coherence, despite the presence of static and dynamic disorder. The present approach combines first-principles parametrized lattice Hamiltonians, based on Time-Dependent Density Functional Theory (TDDFT) and/or high-level electronic structure calculations, with accurate quantum dynamics simulations using the Multi-Configuration Time-Dependent Hartree (MCTDH) method. This contribution specifically addresses the mechanism of charge generation in (i) regioregular oligothiophene-fullerene aggregates, and (ii) highly ordered oligothiophene-perylene diimide co-oligomer assemblies. These studies highlight that chemical design of donor-acceptor combinations needs to account for the effects of electronic delocalization and the modified energetics due to molecular packing, as well as multiple transfer pathways and internal conversion channels induced by vibronic interactions.excitonic states, molecular packing, organic photovoltaics, quantum dynamics, ultrafast charge separation | I N TR ODU C TI ONIn organic donor-acceptor (DA) materials developed for photovoltaics applications, the break-up of photogenerated excitons at DA heterojunction interfaces initiates the irreversible separation of charge carriers. [1,2] Over the past few years, it has become increasingly clear that the efficiency of this process depends on a complex interplay of different factors, such that design principles based on the engineering of molecular structure and DA band offsets are not necessarily sufficient. Indeed, the photochemical processes inherent to the molecular donor and acceptor materials necessitate a molecular-level analysis that may deviate from the basic picture derived from semiconductor physics. This is underscored by an increasing body of evidence from time-resolved spectroscopies [3][4][5][6][7] showing that the elementary energy and charge transfer (CT) processes in typical photovoltaic materials are often of quantum coherent character. Conventional kinetic descriptions are therefore not apt to render a faithful picture of these elementary steps, and may only be valid on longer time scales where hopping type transport dynamics sets in.Even long-range electron-hole separation under the effect of a Coulomb barrier may not necessarily obey the slow, thermally activated dynamics described by the Onsager-Braun model. [8] Indeed, recent time-resolved experiments, for example, for prototypical blends of poly-3-hexylthiophene (P3HT) and the fullerene derivative [6,6]-phenyl-C 61 butyric acid methyl ester (PCBM) and related systems, report ultrafast longrange charge separation, especially in materials exhibiting regioregular morphologies. [9][10][11][12][13][14][15] To explain these ob...

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“…[23][24][25] Because of the potential for controlled assembly driven by thermodynamics dictated by the molecular characteristics of the blocks, CBCP could lead to morphologically stable BHJs. 26,27 For instance, in-plane lamellar order of donor and acceptor domains would provide the interfacial area necessary for charge generation, and at the same time, the p-and n-type transport channels required for efficient collection of photogenerated charge carriers.…”

Section: Introductionmentioning

confidence: 99%

Role of Solution Structure in Self-Assembly of Conjugated Block Copolymer Thin Films

Brady¹,

Ku²,

Pérez³

et al. 2016

Macromolecules

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Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole-terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small angle X-ray scattering with the P3HT block remaining well-solvated.The nanostructure in thin films was determined using a combination of wide and small angle Xray scattering techniques as a function of processing conditions. The solution structure controlled the initial nanostructure in spin-cast thin films allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small angle X-ray scattering. These results suggest the importance of controlling solvent induced aggregation in forming nanostructured thin films of conjugated block co-polymers.

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Challenges and Opportunities in the Development of Conjugated Block Copolymers for Photovoltaics

Cited by 107 publications

References 147 publications

Triplet transport in thin films: fundamentals and applications

Triplet transport in thin films: fundamentals and applications

Quantum dynamical studies of ultrafast charge separation in nanostructured organic polymer materials: Effects of vibronic interactions and molecular packing

Role of Solution Structure in Self-Assembly of Conjugated Block Copolymer Thin Films

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