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DY: Fachverband Dynamik und Statistische Physik

DY 35: Modelling and Simulation of Soft Matter I (joint session CPP/DY)

DY 35.9: Vortrag

Mittwoch, 18. März 2020, 12:00–12:15, ZEU 255

Mesoscopic modeling of disordered morphologies of blends and block-copolymers for light-emitting diodes — •Jianrui Zhang, Kurt Kremer, Jasper Michels, and Kostas Daoulas — Max Planck Institute for Polymer Research, Mainz, Germany

Experiments have demonstrated [1] that the luminous efficiency of polymer light emitting diodes can be significantly increased by blending the semiconducting polymer with an insulator. However, the limited thermodynamic stability of the disordered phase in polymer blends motivates the consideration of alternatives, e.g. block-copolymers (BCPs) comprising semiconducting and insulating blocks. We choose as model systems blends and BCPs of poly(p-phenylene vinylene) (PPV) and polyacrylates. Using a hybrid mesoscopic model, disordered morphologies of these blends and BCPs are obtained with Monte Carlo simulations. We study different compositions and vary the immiscibility to mimick annealing at different temperatures. We find that disordered blends and BCPs are heterogeneous because of fluctuations and local segregation. Local segregation is stronger in BCPs than in their equivalent blends, even though the strength of immiscibility, normalized by the mean-field spinodal, is the same. Using a qualitative charge-percolation model, we link the spatial distribution of PPV with electric conductance. We predict that the annealing temperature affects the electrical percolation in disordered BCPs much stronger than in blends. The observed differences between blends and BCPs are enhanced at high contents of insulator. [1] Abbaszadeh et al., Nature Materials 2016, 15, 628.