Light-Induced EPR Spectroscopy of Charge Transfer in Low-Band-Gap PCDTBT:PC71BM Bulk Heterojunctionsстатья
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Дата последнего поиска статьи во внешних источниках: 8 июня 2022 г.
Аннотация:The light-induced electron paramagnetic resonance (LEPR) study of spin charge carriers steady-state initiated by IR-Vis photons in organic composite of a low-band-gap poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)) with a [6,6]-phenyl-C71-butyric acid methyl ester is reported. Light-Induced Electron Paramagnetic Resonance spectra of the composite were deconvoluted and the main resonance parameters of polarons and anion radicals of methanofullerene were determined. It has shown the reversible formation in polymer backbone of spin traps, whose number, distribution and depth governed by the photon energy. A part of photoinduced charge carriers is pinned by such traps resulting in formation in the composite of polymer and fullerene domains with different band gaps and photon sensitivity. Relaxation and dynamics parameters of spin charge carriers were shown to depend on the energy of exciting photons. The mechanisms of polaron diffusion along and between polymer chains as well as librations of methanofullerene cages in a polymer matrix were proposed. Our results suggest that the use of C70-counter-ions as an electron accepter in the composite provoke its layered morphology. This hinders the formation of spin traps, increases the path length for charge carriers and, therefore, accelerates their spin-assisted relaxation and dynamics through bulk heterojunctions within the visible and infrared regions of the sun spectrum with comparable effectiveness.