Strategy for good dispersion of well-defined tetrapods in semiconducting polymer matrices.

The morphology or dispersion control in inorganic/organic hybrid systems is studied, which consist of monodisperse CdSe tetrapods (TPs) with grafted semiconducting block copolymers with excess polymers of the same type. Tetrapod arm-length and amount of polymer loading are varied in order to find the ideal morphology for hybrid solar cells. Additionally, polymers without anchor groups are mixed with the TPs to study the effect of such anchor groups on the hybrid morphology. A numerical model is developed and Monte Carlo simulations to study the basis of compatibility or dispersibility of TPs in polymer matrices are performed. The simulations show that bare TPs tend to form clusters in the matrix of excess polymers. The clustering is significantly reduced after grafting polymer chains to the TPs, which is confirmed experimentally. Transmission electron microscopy reveals that the block copolymer-TP mixtures ("hybrids") show much better film qualities and TP distributions within the films when compared with the homopolymer-TP mixtures ("blends"), representing massive aggregations and cracks in the films. This grafting-to approach for the modification of TPs significantly improves the dispersion of the TPs in matrices of "excess" polymers up to the arm length of 100 nm.