Effect of Polarization on the Mobility of C<sub>60</sub>: A Kinetic Monte Carlo Study

Volpi, Riccardo; Kottravel, Sathish; Nørby, Morten Steen; Stafström, Sven; Linares, Mathieu

doi:10.1021/acs.jctc.5b00975

Cited by 24 publications

(40 citation statements)

References 50 publications

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“…In contrast to the case on the above-mentioned theoretical approaches used for PEDOT, transport modeling from realistic morphologies obtained by molecular dynamics has been successfully applied to a wide range of organics materials with various levels of theory [28][29][30][31][32][33][34][35][36][37][38][39][40]. The cornerstone of these approaches is the calculation of the transfer integrals distribution in the materials to relate the film morphology to the carrier mobility, highlighting the bottlenecks for charge transport.…”

Section: Introductionmentioning

confidence: 99%

Understanding morphology-mobility dependence in PEDOT:Tos

Rolland

Franco-González

Volpi

et al. 2018

Phys. Rev. Materials

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105

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The potential of conjugated polymers to compete with inorganic materials in the field of semiconductor is conditional on fine-tuning of the charge carriers mobility. The latter is closely related to the material morphology, and various studies have shown that the bottleneck for charge transport is the connectivity between well-ordered crystallites, with a high degree of π -π stacking, dispersed into a disordered matrix. However, at this time there is a lack of theoretical descriptions accounting for this link between morphology and mobility, hindering the development of systematic material designs. Here we propose a computational model to predict charge carriers mobility in conducting polymer PEDOT depending on the physicochemical properties of the system. We start by calculating the morphology using molecular dynamics simulations. Based on the calculated morphology we perform quantum mechanical calculation of the transfer integrals between states in polymer chains and calculate corresponding hopping rates using the Miller-Abrahams formalism. We then construct a transport resistive network, calculate the mobility using a mean-field approach, and analyze the calculated mobility in terms of transfer integrals distributions and percolation thresholds. Our results provide theoretical support for the recent study [Noriega et al., Nat. Mater. 12, 1038] explaining why the mobility in polymers rapidly increases as the chain length is increased and then saturates for sufficiently long chains. Our study also provides the answer to the long-standing question whether the enhancement of the crystallinity is the key to designing high-mobility polymers. We demonstrate, that it is the effective π -π stacking, not the long-range order that is essential for the material design for the enhanced electrical performance. This generic model can compare the mobility of a polymer thin film with different solvent contents, solvent additives, dopant species or polymer characteristics, providing a general framework to design new high mobility conjugated polymer materials.

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Section: Introductionmentioning

confidence: 99%

Understanding morphology-mobility dependence in PEDOT:Tos

Rolland

Franco-González

Volpi

et al. 2018

Phys. Rev. Materials

Self Cite

105

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“…For the explicit formulas used for C and P contribution, we refer the reader to Ref. [ ]. The energetic contribution of the field is explicitly considered with the term

- e \overset{E}{true} \cdot Δ {\overset{r}{true}}_{M N}

.…”

Section: Methodsmentioning

confidence: 99%

“…The external reorganization energy λ out is the reorganization of the environment after the hop and it is approximated with the polarization contribution of the nearby molecules. External reorganization energy is calculated as

λ_{out} = E_{i}^{ind ‐ el} (\underset{s_{2}}{true}, \underset{s_{1}}{true}) + E_{j}^{ind ‐ el} (\underset{s_{2}}{true}, \underset{s_{1}}{true}) - E_{i}^{ind ‐ el} (\underset{s_{2}}{true}, \underset{s_{2}}{true}) - E_{j}^{ind ‐ el} (\underset{s_{2}}{true}, \underset{s_{2}}{true}) .

where

\underset{s_{2}}{true}

is the new state after the hop,

\underset{s_{1}}{true}

is the old state before the hop and

E_{i}^{ind ‐ el} (\underset{s_{2}}{true}, \underset{s_{1}}{true})

is the energy of molecule i after the hop immersed in the polarization before the hop. The other terms can be interpreted analogously.…”

Section: Methodsmentioning

confidence: 99%

Study of the cold charge transfer state separation at the TQ1/PC₇₁BM interface

Volpi

Linares

2017

J Comput Chem

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Charge transfer (CT) state separation is one of the most critical processes in the functioning of an organic solar cell. In this article, we study a bilayer of TQ1 and PC BM molecules presenting disorder at the interface, obtained by means of Molecular Dynamics. The study of the CT state splitting can be first analyzed through the CT state splitting diagram, introduced in a previous work. Through this analysis, we identify the possibility of CT state splitting within Marcus Theory in function of the electric field. Once the right range of electric fields has been identified, we perform Kinetic Monte Carlo simulations to estimate percentages and times for the CT state splitting and the free charge carriers collection. Statistical information extracted from these simulations allows us to highlight the importance of polarization and to test the limits of the predictions given by the CT state splitting diagram. © 2017 Wiley Periodicals, Inc.

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“…A model considering a charge localized on few molecules (but typically one) can be used and this charge is said to be hopping from one site to the next. Kinetic Monte-Carlo (KMC) simulations [35][36][37][38][39][40][41][42][43][44][45] have potentially the capability to model the quantum phenomena happening at the nanoscale, but the more details are included in the KMC scheme the more computational effort is required, limiting detailed KMC schemes to the study of interesting portion of a solar cell. The charge carriers hopping rate in KMC simulations can be calculated in several ways, the most predominantly used in the literature are the Miller-Abrahams rate and the Marcus rate.…”

Section: Modelling Challengesmentioning

confidence: 99%

Modelling Charge Transport for Organic Solar Cells within Marcus Theory

Volpi¹

2017

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The cover is designed by Riccardo Volpi and licensed under the terms of the GNU Free Documentation License. The image of the trajectory of the CT state splitting is created by Sathish Kottravel of the visualization center in Norrköping. As can be noticed, the theory is always hidden in the back. Printed by LiU-Tryck 2017 To the present moment... AbstractWith the technological advancement of modern society, electronic devices are getting progressively more integrated in our everyday lives. Their continuously growing presence is generating numerous concerns about costs, e ciency and the environmental impact of the electronic waste. In this context, organic electronics is finding its way through the market, allowing for potentially low-cost, light, flexible, transparent and environmentally friendly electronics. Despite the numerous successes of organic electronics, the functioning of several categories of organic devices still represents a technological challenge, due to problems like low e ciencies and stabilities (degradation over time). Organic devices are composed by one or more organic materials depending on the particular application. The conformation and electronic structure of the organic molecules as well as their supramolecular arrangement in the single phase or at the interface are known to strongly a↵ect the mobility and/or the e ciency of the device. While there is consensus on the fundamental physics of organic devices, we still lack a detailed comprehensive theory able to fully explain experimental data. In this thesis we focus on trying to expand our knowledge of charge transport in organic materials through theoretical modelling and simulation of organic electronic devices. While the methodology developed is generally valid for any organic device, we will particularly focus on the case represented by organic photovoltaics.The morphology of the system is obtained by molecular dynamics simulations. Marcus theory is used to calculate the hopping rate of the charge carriers and subsequently study the possibility of free charge carriers production in an organic solar cell. The theory is then compared both with Kinetic Monte Carlo simulations and with experiments to identify the main pitfalls of the actual theory and ways to improve it. The Marcus rate between two molecules depends on the molecular orbital energies, the transfer integral between the two molecules and the reorganization energy. The orbital energies and the transfer integrals between two neighbouring molecules are obtained through quantum mechanical calculations in vacuum. Electrostatic e↵ects of the environment are included through atomic v vi charges and atomic polarizabilities, producing a correction both to the orbital energy and to the reorganization energy. We have studied several systems in the single phase (polyphenylene vinylene, C 60 , PC 61 BM, triindoles) and at the interface between two organic materials (anthracene/C 60 , TQ1/PC 71 BM). We show how a combination of di↵erent methodologies can be used to obtain a realistic ...

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Effect of Polarization on the Mobility of C₆₀: A Kinetic Monte Carlo Study

Cited by 24 publications

References 50 publications

Understanding morphology-mobility dependence in PEDOT:Tos

Understanding morphology-mobility dependence in PEDOT:Tos

Study of the cold charge transfer state separation at the TQ1/PC₇₁BM interface

Modelling Charge Transport for Organic Solar Cells within Marcus Theory

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Effect of Polarization on the Mobility of C60: A Kinetic Monte Carlo Study

Cited by 24 publications

References 50 publications

Understanding morphology-mobility dependence in PEDOT:Tos

Understanding morphology-mobility dependence in PEDOT:Tos

Study of the cold charge transfer state separation at the TQ1/PC71BM interface

Modelling Charge Transport for Organic Solar Cells within Marcus Theory

Contact Info

Product

Resources

About

Effect of Polarization on the Mobility of C₆₀: A Kinetic Monte Carlo Study

Study of the cold charge transfer state separation at the TQ1/PC₇₁BM interface