Ultralong 20 Milliseconds Charge Separation Lifetime for Photoilluminated Oligophenylenevinylene–Azafullerene Systems
|Julkaisu||Advanced Functional Materials|
|Varhainen verkossa julkaisun päivämäärä||18 joulukuuta 2017|
|DOI - pysyväislinkit|
|Tila||Julkaistu - helmikuuta 2018|
The synthesis and characterization of oligophenylenevinylene (OPV)–azafullerene (C59N) systems in the form of OPV–C59N donor–acceptor dyad 1 and C59N–OPV–C59N acceptor–donor–acceptor triad 2 is accomplished. Photoinduced electronic interactions between OPV and C59N within 1 and 2 are assessed by UV–vis and photoluminescence. The redox properties of 1 and 2 are investigated, revealing a set of one-electron oxidation and three one-electron reduction processes owed to OPV and C59N, respectively. The electrochemical bandgap for 1 and 2 is calculated as 1.44 and 1.53 eV, respectively, and the free energy for the formation of the charge-separated state for 1 and 2 via the singlet-excited state of OPV is found negative, proving a thermodynamically favorable the process. Photoexcitation assays are performed in toluene and o-dichlorobenzene (oDCB) and the reactions are monitored with time-resolved absorption and emission spectroscopies. Competitive photoinduced energy and electron transfer are identified to occur in both systems, with the former being dominant in 2. Markedly, the charge-separated state in oDCB exhibits a much longer lifetime compared to that in toluene, reaching 20 ms for 1, the highest ever reported value for fullerene-based materials. These unprecedented results are rationalized by considering conformational phenomena affecting the charge-separated state.