Impact of energy alignment and morphology on the efficiency in inorganic–organic hybrid solar cells

Gruber, Manfred; Stickler, Benjamin A.; Trimmel, Gregor; Schürrer, Ferdinand; Zojer, Karin

doi:10.1016/j.orgel.2010.08.015

Cited by 23 publications

(29 citation statements)

References 36 publications

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“…The motion of, for instance, charge carriers in electronic devices is usually modeled on the macroscopic level by a drift-diffusion approach [1][2][3][4][5][6]. The basic equations in such an approach are the current density equation and the continuity equation, which, based on the concept of Brownian motion, relate the current density to the Fokker-Planck equation [6,7].…”

Section: Introductionmentioning

confidence: 99%

Lévy-flight anomalous diffusion in a composite medium

Stickler

Schachinger

2011

Phys. Rev. E

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The one-dimensional Lévy flight in a composite medium consisting of two layers in contact, with arbitrary Lévy indices, is investigated. Such systems are of much interest in the field of organic electronics, where diffusional transport between two materials profoundly influences the device performance. Using the jump-length probability density function for a particular Lévy index as a starting point, equations are derived that describe anomalous diffusion in a composite two-layer medium. Moreover, expressions for the current density are given, and the steady-state distribution for the special case of one dominating diffusion coefficient is illustrated.

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Section: Introductionmentioning

confidence: 99%

Lévy-flight anomalous diffusion in a composite medium

Stickler

Schachinger

2011

Phys. Rev. E

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“…The importance of the device morphology on the efficiency of an organic solar cell (Section 1.2) render very popular theoretical investigations based on simulations. Simulations employing drift-diffusion models [25,32,33] evidence the significant contribution of morphology to the efficiency of solar cells on a global scale, [25,33,34] but with a detail limited by the classical description employed. Since the efficiency of organic solar cells is greatly impacted by the processes that occur at the interface between the donor and acceptor a greater details is desirable.…”

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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“…They can be done at different levels, but for organic electronics they can be divided in two main important categories. A first category of simulations is based on drift-diffusion models [26,32,33]. Some of these studies evidence the significant contribution of morphology to the efficiency of solar cells [26,33,34], but with a detail limited by the classical description employed.…”

Section: Modelling Challengesmentioning

confidence: 99%

“…A first category of simulations is based on drift-diffusion models [26,32,33]. Some of these studies evidence the significant contribution of morphology to the efficiency of solar cells [26,33,34], but with a detail limited by the classical description employed. The second category aim to a quantum mechanical description of the most relevant processes and is based on Monte Carlo simulations, the natural tool to use in studying the dynamic of competing probabilistic events.…”

Section: Modelling Challengesmentioning

confidence: 99%

“…(3.32) In this equation we have introduced the Fock operator 33) this operator can be regarded as an effective one-electron energy operator, including the attractive potential of the nuclei as well as an average of repulsive Coulombic and exchange interactions of the other electrons (with j = i). In particular the exchange interactions enter into the picture as a purely quantum mechanical effect coming from the Slater determinant form of the wave function for identical fermions.…”

Section: Hartree-fock 23mentioning

confidence: 99%

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Charge Transport Simulations for Organic Electronics: A Kinetic Monte Carlo Approach

Volpi¹

2016

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In this thesis we focus on the modelling and simulation of organic electronic devices, investigating their structural and electronic properties. Organic devices have attracted great interest for their innovative properties, but their functioning still represent a theoretical and technological challenge. They are composed by one or more organic materials depending on the particular application. The morphology of organic devices in the single phase or at the interface is known to strongly determine mobility and efficiency of the devices. The structural disorder is studied through molecular dynamics (MD) simulations. Marcus formula is used to calculate the hopping rate of the charge carriers and the model developed is tested by simulations in a Kinetic Monte Carlo scheme. The dependence of the transfer integrals on the relative molecular orientation is achieved through a weighted Mulliken formula or through a dimer projection approach using the semi-empirical Hartree Fock method ZINDO. Electrostatic effects, have been included through atomic charges and atomic polarizabilities, calculated at the B3LYP level of theory. The inclusion of electrostatic effects has been shown (through simulations in 4PV and C 60 ) to be crucial to obtain a good qualitative agreement with experiments, for both mobility field and temperature dependence in the single phase. In particular the external reorganization energy, calculated through the polarization of the environment, has been shown to have a great impact on the conduction, shifting the inverse Marcus region and helping CT state separation at the interface (between C 60 and anthracene).iii iv

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Impact of energy alignment and morphology on the efficiency in inorganic–organic hybrid solar cells

Cited by 23 publications

References 36 publications

Lévy-flight anomalous diffusion in a composite medium

Lévy-flight anomalous diffusion in a composite medium

Modelling Charge Transport for Organic Solar Cells within Marcus Theory

Charge Transport Simulations for Organic Electronics: A Kinetic Monte Carlo Approach

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