Modelling the effect of the structure of polymer photocells on their absorption spectrum

A framework for the calculation of light absorption in multi-component polymer photocells is presented. It is tested on a modelled periodic lateral structure of two polyfluorene conjugated polymers with complementary absorption spectra. It is shown how the coupling induced by scattering at the interfaces between different regions of the structure leads to enhanced absorption arising from energy flow from the less absorbing to the more absorbing material. We also show that a periodic structure can lead to resonance amplification of absorption in part of the absorption spectrum. These lead to an enhancement in the calculated absorption spectrum by up to 2.6 times. It is further show that a periodic lateral structure can show larger optical absorption than similar devices with a bilayer structure. This method is generally applicable to multi-component heterojunction photovoltaic diodes.