Investigation of ultrafast dynamics in dye-sensitized solar cells by two-dimensional electronic spectroscopy

In this work we are investigating the ultrafast photo-induced processes relevant for the function and power conversion efficiency (PCE) of transparent near-infrared dye-sensitized solar cells. The cell design consists of a semiconducting (SC) layer (TiO2 or Al2O3), on which the dye molecules (pyrrolopyrrole cyanine TB336) are covalently bound, and an electrolyte for the charge regeneration of the dyes. To study the complex dynamics that lead to photocurrent we use an advanced implementation of Two-Dimensional Electronic Spectroscopy (2DES), with sub-7fs pump pulses spanning the TB336 absorption spectrum (650-850 nm), and white-light probing (400-900 nm). This technique can therefore distinguish precisely the cation generation efficiency of monomers and dimers, respectively. First results indicate an unexpected red-shift of the action spectrum of cation generation, as compared to the total absorption spectrum of the cells. Future experiments will verify this finding for solar cells with different dye concentrations.