How Efficient Is Electron Collection in Dye-Sensitized Solar Cells? Comparison of Different Dynamic Methods for the Determination of the Electron Diffusion Length

Abstract

The diffusion length of electrons in high efficiency liquid electrolyte dye-sensitized nanocrystalline solar cells has been investigated using two different approaches. The first method is based on measuring the rise and decay times of the small amplitude photovoltage increment generated by a short laser pulse superimposed on a range of steady-state illumination levels. The advantage of this technique is that it allows the simultaneous measurement of the diffusion coefficient and electron lifetime under identical conditions. In addition to transport-controlled substrate charging, direct injection of electrons into the substrate from dye adsorbed at the contact interface was observed at the high laser pulse energies required for measurements at high dc photovoltages. The second method involves using intensity-modulated photocurrent and photovoltage spectroscopies (IMPS and IMVS, respectively) to measure the electron diffusion coefficient and electron lifetime at short circuit and open circuit, respectively...