Re-evaluation of Recombination Losses in Dye-Sensitized Cells: The Failure of Dynamic Relaxation Methods to Correctly Predict Diffusion Length in Nanoporous Photoelectrodes

Abstract

Photocurrents generated by thick, strongly absorbing, dye-sensitized cells were reduced when the electrolyte iodine concentration was increased. Electron diffusion lengths measured using common transient techniques (L(n)) were at least two times higher than diffusion lengths measured at steady state (L(IPCE)). Charge collection efficiency calculated using L(n) seriously overpredicted photocurrent, while L(IPCE) correctly predicted photocurrent. This has implications for optimizing cell design.

Enhanced Electron Collection Efficiency in Dye-Sensitized Solar Cells Based on Nanostructured TiO2 Hollow Fibers

“…Besides, the electron transport lifetime τ n within the oxide network to the back contact was obtained by recording the rise time of the perturbed open circuit photovoltage. 21,22 Between each point and before the white LEDs switched to the next intensity, a charge extraction routine was executed by rapidly short circuiting the cell.…”

Diffusion length in nanoporous TiO2 films under above-band-gap illumination

“…It has been explicitly demonstrated that the diffusion length is the key parameters maximizing the charge collection efficiency. [10][11][12][13] Both transient and steady-state methods have been used to determine the electron diffusion length in DSCs. [12][13][14][15][16][17] In both these approaches, the diffusion lengths are measured indirectly, which requires appropriate modeling and exact knowledge of other optical parameters.…”

“…[10][11][12][13] Both transient and steady-state methods have been used to determine the electron diffusion length in DSCs. [12][13][14][15][16][17] In both these approaches, the diffusion lengths are measured indirectly, which requires appropriate modeling and exact knowledge of other optical parameters. Recently, scanning photocurrent microscopy (SPCM) has been proven to be a very effective tool for addressing the diffusion length in DSCs, without the knowledge of additional parameters.…”

High-Efficiency Dye-Sensitized Solar Cell with Three-Dimensional Photoanode

“…Finally, enhancing the electron transport could improve charge collection and reduce IR losses, enhance the short-circuit current, and fill factor. 12, 18 Several approaches have been proposed in order to reduce interfacial recombination and improve charge collection in liquid electrolytes and ss-DSCs including the use of radial collection nanostructures, 7 one-dimensional ZnO and TiO 2 nanorods, and nanowires as photoanodes. 22À25 Even though these approaches show great promise, they have yet to achieve power conversion efficiencies above 5% in liquid electrolyte DSCs and 1.7% in ssDSCs.…”