Short-pulsed lasers, delayed extraction

Fig. 20 Determination of the coefficient of bimolecular recombination by performing TDCF experiments with variable delay between the excitation pulse and application of the collection bias, (a) Scheme of the experiment, (b) Experimental TDCF photocurrent transients (open squares) measured on a 200 nm thick layer of slow-dried POFTTiPCBM (1 1) during application of different collection biases Fcoii- The collection bias was applied 150 ns after the laser pulse (t = 0 in this graph). Solid lines show fits to the data using a numerical drift diffusion model with constant electron and hole mobilities. A noteworthy observation is that charges can be fully extracted from these layers within a few hundreds of nanoseconds for a sufficiently high collection bias [171]. (c-f) Q-pre, 2coii> and 2,o, plotted as a function of the delay time for as-prepared and thermally annealed chloroform-cast P3F1T PCBM, and with the pre-bias Fpre set either to 0.55 V (near open circuit) or to 0 V (short-circuit conditions) [172]. Solid lines show fits with an iterative model that considers bimolecular recombination of free charges in competition with their extraction...

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