Studies of Photoinduced Charge Carrier Dynamics in Conjugated Polymers
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This study explores the morphology and charge carrier dynamics in bulk heterojunctions (BHJs) of donor polymers and molecular acceptors. We analyze the effects of polymer-nonfullerene acceptor (NFA) blend composition on morphology, energetics, recombination kinetics, and photocurrent properties. Altering film composition results in varying morphologies from highly intermixed to a combination of intermixed and pure phases. Transient absorption spectroscopy shows that an energetic cascade between phases is crucial for effective electron-hole separation. Increased NFA electron affinity in pure phases is linked to structural changes, enhancing charge separation and collection. High crystallinity in blends leads to efficient charge transfer state dissociation. These findings highlight the importance of high crystallinity and long exciton diffusion lengths for optimal performance in organic solar cells.