Chemical diffusion coefficient in dye sensitized solar cells as a function of porosity and surface roughness

The distribution and diffusion behaviors of microscopic particles at fluorobenzene–water and pentanol–water interfaces are investigated using molecular dynamics simulation. The influences of Na+/Cl− ions and the steric effects of organic molecules are examined. The concentration distributions of different species, the orientations of oil molecules at the interface, and oil–water interface morphology as well as the diffusion behaviors of water molecules are explored and analyzed. The results indicate that a few fluorobenzene molecules move into the water phase influenced by Na+/Cl− ions, while the pentanol molecules at the interface prefer orientating their hydrophilic groups toward the water phase due to their large size. The water molecules more easily burst into the pentanol phase with larger molecular spaces. As the concentration of ions in the water phase increases, more water molecules enter into the pentanol molecules, leading to larger interface roughness and interface thickness. In addition, a lower diffusion coefficient for water molecules at the fluorobenzene–water interface are observed when introducing Na+/Cl− ions in the water phase, while for the pentanol–water system, the mobility of interfacial water molecules are enhanced with less ions and inhibited with more ions.

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“…On this basis, the diffusion coefficient ( D ) of water molecules at the interface is calculated as following [28]:D=16truelimt→∞dMSDdt…”

Section: Resultsmentioning

confidence: 99%

Molecular Dynamics Simulation of Distribution and Diffusion Behaviour of Oil–Water Interfaces

Zhang

Dai

et al. 2019

Molecules

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“…This meant that oxidized/reduced molecular charges on one particle could only interact with electrocatalysts on that same particle, overall resulting in more restrictive percolation zones than present in actual mesoporous thin films. Performing Monte Carlo simulations where electron-transfer events between particles are allowed to occur is not a new concept ,− but the detailed functionality and inclusion of discrete dyes and electrocatalysts are unique to our model, therefore enabling a better understanding of design rules for these functional constructs.…”

Section: Experimental Sectionmentioning

confidence: 99%

“…Several groups have modeled thin films of dye-sensitized semiconducting nanoparticles as detailed three-dimensional mesoporous networks of spheres to simulate electron transport within the semiconducting materials and interfacial electron-transfer recombination processes. − However, in none of those works was surface-confined electron transfer between redox-active molecules anchored to the nanoparticle surfaces considered. Uniquely, only Meyer and co-workers simulated electron-transfer processes between molecules surface-anchored to a three-dimensional structure consisting of a regular array of spherical nanoparticles using a discrete-time random walk Monte Carlo method .…”

Section: Introductionmentioning

confidence: 99%

Numerical Monte Carlo Simulations to Evaluate the Influence That Spherical Nanoparticle Size and Arrangement Have on Interparticle Charge Transport across the Surface of Dye- and Cocatalyst-Modified Materials

Tkaczibson

Ardo

2020

ACS Appl. Energy Mater.

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Mechanistic information underlying the function of illuminated mesoporous thin films of nanomaterials that contain distinct light-absorbing and electrocatalytic units can be gleaned from discrete-time random walk Monte Carlo simulations. These simulations bridge the length and time scales between individual electron-transfer events and ensemble behavior observed from bulk thin films. Most simulations are performed using models that simplify random mesoporous networks as isolated spherical nanoparticles. However, these simplifications may not provide sufficient detail to capture macroscopic experimental observations, especially when mesoporous nanomaterials consist of various geometries. Herein, we examine the role that the structure of the mesoporous thin film plays on the ability of photogenerated charges to accumulate on surface-confined redox-active electrocatalysts that require two redox events for turnover. We observe that the structure has a dramatic influence on the expected spectroscopic absorption anisotropy signal over time. We also observe that the yield for electrocatalyst turnover, as a function of the ratio of the electron-transfer time constant for self-exchange reactions and charge recombination time constant between the semiconducting mesoporous thin film and an oxidized/reduced surface-confined dye or electrocatalyst, is influenced by the total surface coverage of redox-active species. Structures consisting of spherical nanoparticles that are barely touching or partially necked are more effective at electrocatalytic turnover in the presence of vacant sites than discrete spherical nanoparticles or those that are arranged in a rodlike structure. Moreover, we show that the yield for electrocatalyst turnover is nearly independent of whether the simulations are performed on complex three-dimensional structures or simple two-dimensional planar grids. This discovery suggests that the added complexity of three-dimensional models may not be necessary to explain differences in electrocatalytic turnover yield in photoelectrochemical constructs containing surface-confined light-absorbing and electrocatalytic units.

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“…24 Also, Abdi et al have introduced equations describing the morphological dependency of electron transport in nanostructured solar cells. 25 The mentioned previous reports on the morphology-dependent electron transport are applicable just for semiconductor media in which the limiting parameter for charge transport is only porosity. On the other hand, there are some reports on the simulation of charge transport in organic solar cells.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation for Investigation of Morphology Dependent Charge Transport in Bulk-Heterojunction Organic Solar Cells

Taherpour

Abdi

2018

J. Phys. Chem. C

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Morphology, the spatial distribution of traps, interdomain connectivity, and phase separation of the active layer play a critical role in the performance of the bulk heterojunction (BHJ) organic solar cells (OSCs). In this work, we utilize the hopping transport model to simulate the effect of morphological and structural parameters on the diffusion coefficient and efficiency of the polymer-fullerene BHJ solar cells. In BHJ solar cells there are two distinct phases as electron transport material (acceptor) and hole transport material (donor). Here we try to create an almost realistic network containing P3HT polymer chains and PCBM clusters for simulating the charge transport in the active layer. The blend ratio of P3HT:PCBM polymers and alignment of these bicontinuous networks of active layer are considered here as the morphological parameter affecting the cell performance. The dependency of the charge transport on such morphological parameters is obtained in this study by using Monte Carlo continues time random walk simulations.

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Chemical diffusion coefficient in dye sensitized solar cells as a function of porosity and surface roughness

Cited by 8 publications

References 26 publications

Molecular Dynamics Simulation of Distribution and Diffusion Behaviour of Oil–Water Interfaces

Molecular Dynamics Simulation of Distribution and Diffusion Behaviour of Oil–Water Interfaces

Numerical Monte Carlo Simulations to Evaluate the Influence That Spherical Nanoparticle Size and Arrangement Have on Interparticle Charge Transport across the Surface of Dye- and Cocatalyst-Modified Materials

Monte Carlo Simulation for Investigation of Morphology Dependent Charge Transport in Bulk-Heterojunction Organic Solar Cells

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