Investigation of the exciton relaxation processes in poly(9,9-dioctylfluorene- co -benzothiadiazole):CsPbI 1.5 Br 1.5 nanocrystal hybrid polymer-perovskite nanocrystal blend.

The combination of lead halide perovskite nanocrystals and conjugated polymer in a blend film opens the way to the realization of hybrid active layers with widely tunable optical and electrical properties. However, the interaction between the polymeric and the perovskite component of the blends is mainly unexplored to date. In this work we perform temperature-dependent photoluminescence and time resolved photoluminescence measurements in order to deeply investigate the photophysics of a poly(9,9-dioctylfluorene- co -benzothiadiazole) (F8BT):CsPbI 1.5 Br 1.5 nanocrystal hybrid film. Our results suggest that the primary interaction channel is charge transfer, both from F8BT to the NCs and from the NCs to F8BT, while Förster resonant energy transfer has no visible effects. Moreover, we show that the charge transfer is assisted by energy migration within the F8BT excited state distribution and that it is dependent on the local micromorphology of the film. Our work improves the current understanding of the polymer:perovskite NC interactions in hybrid films, and it is expected to be relevant for the development of hybrid organic-perovskite optoelectronic devices.