Revealing Complex Relaxation Processes of Collapsed Conjugated Polymer Nanoparticles in the Presence of Different Shapes of Gold Nanoparticles Using Global and Target Analysis
Arnab Ghosh, Srijon Ghosh, Goutam Ghosh, Bikash Jana, Amitava Patra
Abstract
Heterostructures of polymer and metal nanoparticles are extensively used in optoelectronic and light-harvesting depending on their charge transfer kinetics. Here, we investigate the influence of the shape of metal nanoparticles on the carrier relaxation processes of polymer nanoparticles (PNP) in poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT)-Au nanoparticle heterostructures using ultrafast transient absorption spectroscopy. Global and target analysis of transient absorption data is used to reveal the relaxation processes of hot singlet state, singlet state, and delocalized collective state of polymer nanoparticles in the presence of Au nanoparticles (NP), and Au nanorods (NR). In the case of Au NP, the energy transfer takes place from the hot singlet excited state (∼680 fs), and ultrafast electron transfer takes place from both the singlet excited state (∼5 ps) and collective delocalized state (∼26.2 ps) of F8BT polymer nanoparticles to Au NP. However, the very fast energy transfer from the singlet excited state (<125 fs) and ultrafast electron transfer (∼188 fs) from the singlet excited state of F8BT PNP are found in the presence of Au NR. Again, the diffusion length (LD) of F8BT PNP has changed from ∼1.97 to ∼1.65 nm in the presence of Au NP and ∼1.55 nm in the presence of Au NR. Thus, the shape of the metal nanoparticles plays an important role to control the charge transfer dynamics, which is decisive for designing efficient organic–inorganic heterostructure light-harvesting systems.