Investigation of Recombination in Organic Heterostructures by I-Celiv

In this work, we propose the experimental technique for the estimation of the recombination rate at the interface between hole and electron transporting layers. This technique could be used in dye sensitized solar cells where a very thin generation layer is placed between transporting layers. The proposed technique is based on the extraction of injected charge carriers and the determination of the dependence of the amount of the extracted charge on the density of injection current. We present the analytical solution of this dependence for two different cases: low recombination rate, when charge carriers accumulate at the interface, and fast recombination rate. The dependencies for moderate recombination rates and in the presence of the intermediate layer have been investigated by the numerical modeling. With the help of the proposed technique, the interface recombination rates were determined experimentally in the sandwich structures of TiO2/P3HT and TiO2/Spiro-MeOTAD. The technique has also been used in the investigation of recombination processes in TiO2/perovskite/Spiro-MeOTAD solar cells.