Abstract

Considerable attention is today devoted to the engineering of films widely used in photocatalytic, solar energy converters, photochemical and photoelectrochemical cells, dye-sensitized solar cells (DSSCs), to optimize electronic time response following photogeneration. However, the precise nature of transport processes in these systems has remained unresolved. To investigate such aspects of carrier dynamics, we have suggested a model for the calculation of correlation functions, expressed as the Fourier transform of the frequency-dependent complex conductivity σ(ω). Results are presented for the velocity correlation functions, the mean square deviation of position and the diffusion coefficient in systems, like TiO2 and doped Si, of large interest in present devices. Fast diffusion occurs in short time intervals of the order of few collision times. Consequences for efficiency of this fast response are discussed in relation to nanostructured devices.

Highlights

  • Considerable attention is today devoted to the engineering of films widely used in photocatalytic, solar energy converters, photochemical and photoelectrochemical cells, dye-sensitized solar cells (DSSCs), to optimize electronic time response following photogeneration

  • If the mean free path of charges due to scattering phenomena is larger than the particle dimensions, one has a mesoscopic system, in which the transport depends on dimensions and one might correct the transport bulk theories by considering this phenomenon

  • To establish the applicability limit of a bulk model and to investigate the time response of systems at nanoscale we have performed a new approach based on correlation functions obtained by a Fourier transform of the frequency-dependent complex conductivity of the system [1]

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Summary

Introduction

Considerable attention is today devoted to the engineering of films widely used in photocatalytic, solar energy converters, photochemical and photoelectrochemical cells, dye-sensitized solar cells (DSSCs), to optimize electronic time response following photogeneration. To establish the applicability limit of a bulk model and to investigate the time response of systems at nanoscale we have performed a new approach based on correlation functions obtained by a Fourier transform of the frequency-dependent complex conductivity of the system [1]. Starting from the Drude–Lorentz model [4,5] we have obtained directly the correlation function of velocities, the quadratic average distance crossed by the charges as a function of time and the diffusion coefficient D.

Results
Conclusion

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