Transient emission studies of electron injection in dye sensitised solar cells

Time resolved single photon counting is employed to monitor electron injection dynamics in dye sensitised solar cells. It is shown that, by the use of a non-injecting reference film and a simple stretched exponential fitting procedure with only two fitting parameters it is possible to resolve electron injection half-times down to 60 ps resolution. This provides a potentially cheaper and experimentally easier approach to monitor such dynamics compared to more widely used ultrafast pump/probe laser spectroscopy. Injection dynamics are observed for a range of different sensitiser dyes and redox electrolytes. As expected, the presence of a redox electrolyte results in a significant retardation of the injection half-times relative to an inert, aprotic solvent, with typical injection half-times being in the range 120-3000 ps depending upon sensitiser dye employed. In all cases, the injection dynamics fitted well to the stretched exponential function, consistent with a numerical model based upon inhomogeneous energetics of electron injection.