Abstract
We report ultrafast transient UV–vis absorption and electrochemical spectroscopies on the photoinduced charge separation dynamics in a recently synthesized family of metal-free donor–acceptor syste...
Highlights
A photosensitizer is a molecular group that by absorbing UV− vis radiation triggers a physicochemical reaction in adjacent moieties or neighboring molecules by energy, electron, or charge transfer from its excited state
We report on the photoinduced charge separation dynamics in a recently synthesized family of metal-free tunable donor−acceptor systems,[32,36] where two redox-active molecules are fused into a compact and planar structure upon annulation of a tetrathiafulvalene to a benzothiadiazole as a donor and acceptor, respectively
We found an outstanding tunability of the lifetime of the photoinduced charge separation by more than 2 orders of magnitude upon minimal changes of the periphery residues of the acceptor and polarity of the environment
Summary
A photosensitizer is a molecular group that by absorbing UV− vis radiation triggers a physicochemical reaction in adjacent moieties or neighboring molecules by energy, electron, or charge transfer from its excited state. Two points make it worthwhile to look for alternatives: (1) the low abundance on Earth of the most used metals (Ru, Re, Pt, Ir) could set a limit to a massive usage of technologies based on them; (2) from a more fundamental point of view, the main drawback of such compounds is the presence of very efficient intersystem crossing (ISC) processes, which make the photoexcitable singlet state convert very quickly (often within tens of fs)[14−16] to lower energy triplet or even quintet states This degradation of the electronic energy into vibrational energy results in a decrease of the available driving force for the physicochemical reaction. Without the fast ISC process, the overall losses would be only 0.5 eV
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