Monte Carlo Random Walk Simulation of Electron Transport in Dye-Sensitized Nanocrystalline Solar Cells: Influence of Morphology and Trap Distribution

Abstract

Electron transport in the porous nanostructured titanium oxide, as a main concern in the dye-sensitized solar cells, was investigated by random walk simulation. Geometrically disordered nanoparticle networks with random distribution of energy was generated and utilized for simulations. Dependency of the diffusion coefficient (D ef ) on the nanoparticles size, grains connectivity, and the network porosity was completely studied in two cases: traps are placed mainly on the surface or in the volume of the nanoparticles. It was shown that the D ef is independent of nanoparticle size for both surface and volume diffusion. We have shown in this study that increasing the D ef with the particle size is a consequence of the trap-filling (electronic) effect and not a geometrical effect. The role of electronic effect in electron transport in nanoporous materials has been highlighted in this work.

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

“…2c and d represents the diffusion coefficient and conductance versus the surface roughness, f. As shown in these figures at a constant fermi level, electron transport is independent of surface roughness. The same results can be obtained by MT model which have been carried out previously (Ansari-Rad et al, 2012;Frank et al, 2004). It was shown by Ansari-Rad et al that D n is independent of f at the constant Fermi level.…”

“…In the previous works (Anta and Morales-Flórez, 2008;Abdi et al, 2014;Ansari-Rad et al, 2012;Cass et al, 2003Cass et al, , 2005Bisquert, 2004;Tessler et al, 2009) dependency of the chemical diffusion coefficient on the morphological parameters was reported. The main advantage of this work is obtaining the porosity/surface roughness dependent equations for the chemical diffusion coefficient.…”

“…Experimental investigations show that the electrical characteristics of the cells depend on the morphological parameters (Kopidakis et al, 2005;Nakade et al, 2003). Monte-Carlo random walk (MCRW) simulations was recently used to study electron transport in porous media (Anta and Morales-Flórez, 2008;Abdi et al, 2014;Ansari-Rad et al, 2012). Cass et al (2003Cass et al ( , 2005 have studied the effect of the electrical connectivity between the nanoparticles on the transport properties of the electrons.…”

Investigation of Electron Behavior in Nano‐TiO2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements

“…[7][8][9][10][11][12] Although great progress has been made in the fabrication of various highly active materials, few efforts have been made to study the fundamental knowledge of photocatalysis. As photocatalysis includes many physicochemical processes, [13][14][15][16][17][18] it is so complicated that its thermodynamic and dynamic mechanisms are still unclear to date. In general, it is considered that the oxidation ability of holes drives the occurrence of photocatalysis from the thermodynamic viewpoint, [19][20][21] but the role of electrons in photocatalysis has not been described.…”

Tin oxide based dye sensitized solar cells

“…First of all, classic mechanics modelling has been employed in DSSC in which charges injection into semiconductor are assume to behave like a classical particles when study of the transportation of the charges across the semiconductor. [82,83] Next, optical modelling used to examine the light scattering path ways across the semiconductor oxide layer. [84,85] It helps in guiding to design an effective semiconductor layer to maximize the light absorption to increase the PCE of DSSC.…”