Excitons delayed photoluminescence

We show that the exciplex states that form at the interface between F8 and PFB can be thermally excited to form bulk excitons. This is observed as delayed PFB exciton emission in time-resolved photoluminescence measurements. These findings are analogous to those presented for PFB F8BT and TFB F8BT interfaces in the previous section and therefore support the generality of the phenomenon of endothermic exciplex-to-exciton energy transfer in polyfluorene blends. 

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