Structure optimization of organic planar heterojunction solar cells

The management of light absorption in organic photovoltaic cells is of great importance for exciton generation and thus photocurrent. Sufficient light harvesting can be established by localizing the maxima of light absorption density in the region of active layer. Using organic photovoltaic (OPV) devices based on copper phthalocyanine (CuPc) and bulkfullerene (C60) as an example, we demonstrate the methods for localizing the optical interference peaks of the main absorbed light wavelengths inside the respective active layers. The fundamental regulations of the electromagnetic field distribution with thicknesses of the active layers are clarified. The influence of the thickness of the cathode buffer layer on the optimized active layer thicknesses is discussed. Exciton diffusion modelling is combined with optical modelling to give theoretically optimized device structures. The consistency between the results of simulation and experiments is shown, which indicates the validation of the guidance of the modelling work presented in this paper for the design of effective light-using OPV devices.