Do electrons diffusing in a nanostructured semiconductor have time to attain local equilibrium?

• Published in: Solar energy materials and solar cells 2020-09, Vol.215, p.110687, Article 110687
• Main Authors: Freire, José A., Emidio, Guilherme A.
• Format: Article
• Language: English
• Subjects: Balancing; Chemical potential; Cytology; Diffusion coefficient; Dye-sensitized solar cell; Dye-sensitized solar cells; Electron diffusion; Electron traps; Local equilibrium; Morphology; Nanoparticles; Nanostructure; Photovoltaic cells; Solar cells; Transit time; Traps
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2020.110687

The electron diffusion in the nanostructured photoanode of a dye-sensitized solar cell is affected by both the nanoparticle film morphology and the electron traps in the nanoparticles. The effect of the traps is to reduce the diffusion coefficient from its trap free value, which is deleterious to the cell performance. However, there is a time for the effect of the traps to be felt, which can be identified with a local or quasi equilibration time. We address this issue here and show how the volume of the nanoparticles, the equilibrium chemical potential and the temperature affect this time and can make the local equilibration time comparable to the electron transit time across the film. [Display omitted] •A master equation model was proposed to explain the electron equilibration process.•The time for local equilibrium was investigated.•How the time for local equilibrium compares with the transit time was revealed.•A relation between diffusion and electron decay at global equilibrium was identified.