Fullerenecrystallisation as a key driver of charge separation in polymer/fullerene bulk heterojunction solar cells

Jamieson, Fiona C.; Domingo, Ester Buchaca; McCarthy-Ward, Thomas; Heeney, Martin; Stingelin, Natalie; Durrant, James R.

doi:10.1039/c1sc00674f

Cited by 424 publications

(579 citation statements)

References 61 publications

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“…Based on these results, the authors proposed that electron delocalisation due to the existence of fullerene clusters is of critical importance for efficient free carrier generation (Figure 9b). 127 This finding is consistent with the ubiquitous use of fullerene in highly efficient devices, and supported by the electronic structure calculations on large fullerene clusters. 128 In addition, Falke et al showed that coherent electron-nuclear motion might play a key role in charge delocalization over the polymer-fullerene interfaces.…”

Section: The Role Of Charge Delocalisation On Free Charge Generationsupporting

confidence: 80%

Charge generation in polymer–fullerene bulk-heterojunction solar cells

Gao

Inganäs

2014

Phys. Chem. Chem. Phys.

204

252

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Charge generation in organic solar cells is a fundamental yet heavily debated issue. This article gives a balanced review of different mechanisms proposed to explain efficient charge generation in polymer-fullerene bulk-heterojunction solar cells. We discuss the effect of charge-transfer states, excess energy, external electric field, temperature, disorder of the materials, and delocalisation of the charge carriers on charge generation. Although a general consensus has not been reached yet, recent findings, based on both steady-state and transient measurements, have significantly advanced our understanding of this process.2

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Section: The Role Of Charge Delocalisation On Free Charge Generationsupporting

confidence: 80%

Charge generation in polymer–fullerene bulk-heterojunction solar cells

Gao

Inganäs

2014

Phys. Chem. Chem. Phys.

204

252

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“…[19][20][21][22][23] This has strong implications on the photophysics of the materials. [24][25][26][27][28][29][30] In the present contribution, we demonstrate that the dynamics of charge generation in polymer:fullerene blends is largely determined by the microstructure. To that aim, we have used femtosecond transient absorption (TA) spectroscopy to investigate CS in several systems with well-characterized BHJ structure.…”

Section: Introductionmentioning

confidence: 85%

The influence of microstructure on charge separation dynamics in organic bulk heterojunction materials for solar cell applications

et al. 2014

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Light-induced charge formation is essential for the generation of photocurrent in organic solar cells. In order to gain a better understanding of this complex process, we have investigated the femtosecond dynamics of charge separation upon selective excitation of either the fullerene or the polymer in different bulk heterojunction blends with well-characterized microstructure. Blends of the pBTTT and PBDTTPD polymers with PCBM gave us access to three different scenarios: either a single intermixed phase, an intermixed phase with additional pure PCBM clusters, or a three-phase microstructure of pure polymer aggregates, pure fullerene clusters and intermixed regions. We found that ultrafast charge separation (by electron or hole transfer) occurs predominantly in intermixed regions, while charges are generated more slowly from excitons in pure domains that require diffusion to a charge generation site.The pure domains are helpful to prevent geminate charge recombination, but they must be sufficiently small not to become exciton traps. By varying the polymer packing, backbone planarity and chain length, we have shown that exciton diffusion out of small polymer aggregates in the highly efficient PBDTTPD:PCBM blend occurs within the same chain and is helped by delocalization.

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“…Absent at sharp heterojunctions, this type of interphase has been found to improve exciton yield in polymer-fullerene devices [190,191] -i.e., disorder appeared to be of advantage. We expand on this observation and study, as a proof of concept, small protrusions of C 60 into a D5M domain.…”

Section: The Role Of Interfacial Defectsmentioning

confidence: 99%

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

Poelking

2018

Springer Theses

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The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors The rational design of organic semiconductors for optoelectronic devices relies on a detailed understanding of how their molecular and morphological structure condition the energetics and dynamics of charged and excitonic states. Investigating the role of molecular architecture, conformation, orientation and packing, this work reveals mechanisms that shape the spatially resolved densities of states in organic, small-molecular and polymeric heterostructures and mesophases. The underlying computational framework combines multiscale simulations of the material morphology at atomistic and coarse-grained resolution with a long-range-polarized embedding technique to resolve the electronic structure of the molecular solid. We show that longrange electrostatic interactions tie the energetics of microscopic states to the mesoscopic structure, with a qualitative and quantitative impact on charge-carrier level profiles across organic interfaces. The computational approach provides quantitative access to the charge-density-dependent opencircuit voltage of planar heterojunctions. The derived and experimentally verified relationships between molecular orientation, architecture, level profiles and open-circuit voltage rationalize the acceptor-donor-acceptor pattern for donor materials in high-performing solar cells. Proposing a pathway for barrier-less dissociation of charge transfer states, we highlight how mesoscale fields generate charge splitting and detrapping forces in systems with finite interface roughness. The associated design rules reflect the dominant role played by lowest-energy configurations at the interface. Acknowledgements 121 Die (nicht-)lokale Zustandsdichte elektronischer Anregungen in organischen Halbleitern List of Publications 123Bibliography 125 Chapter 1 Organic Electronics in a NutshellThe discovery of conductive polymers in the 1970s [1,2] -rewarded with the Nobel prize in chemistry in the year 2000 -and subsequent development of the first polymeric electronic devices in the 1980s [3-5] have marked the beginnings of a vast interdisciplinary research field referred to as organic electronics. Drawing from both polymeric and small-molecular semiconductors, organic thin-film transistors, solar cells, light-emitting diodes, photodetectors and sensors name just a few out of many applications that make use of the supreme chemical versatility and mechanical flexibility of the underlying "soft" molecular materials. Furthermore enabling low-temperature solution-based processing, printing and spray coating, organic electronics is set to complement the conventional silicon-based electronics in diverse waysadding functionality and improving sustainability. This introductory chapter will provide a short review of the materials and device physics, as well as of new trends and challenges that emerged in the field over the past decade. MaterialsOrganic semiconductors are molecular materials that exist at the interface between orga...

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Fullerenecrystallisation as a key driver of charge separation in polymer/fullerene bulk heterojunction solar cells

Cited by 424 publications

References 61 publications

Charge generation in polymer–fullerene bulk-heterojunction solar cells

Charge generation in polymer–fullerene bulk-heterojunction solar cells

The influence of microstructure on charge separation dynamics in organic bulk heterojunction materials for solar cell applications

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

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