<p>Side-chain
substitutions have important influence on the aggregation of perylene diimide
(PDI), which show a great impact on their excited-state dynamics as well.
Herein, by employing photoluminescence (PL), time-resolved photoluminescence
(TRPL) and transient absorption (TA) spectroscopy, we investigated
excited-state dynamics of two perylene diimide (PDI) derivative amorphous
films, i.e. undecane-substituted PDI (PDI-1) and diisopropylphenyl-substituted
PDI (PDI-2), fabricated with spin coating method. Femtosecond transient absorption spectra reveal that
both films show pronounced ground state bleach (GSB) with lifetime longer than
10 ns while the relaxation of excited state absorption (ESA) has typical
lifetime less than 1 ns. The significant feature of excited state decay in
PDI-2 is dominated by transforming the singlet excited state into two triplet
states via singlet fission, which is evidenced by the appearance of triplet
state absorption. By contrast, the absence of triplet state absorption and the appearance
of long-lived emission species in PDI-1 suggest that the decay of excited-like
state could be dominated by the formation of excimer.
Our present study reveals for the first time that the singlet fission does
occur in amorphous PDI film,
the study also demonstrates that side-chain
substitutions have great impact on the excited-state dynamics of PDI. </p>
Impact of Side-Chain Substituents on the Excited State Dynamics of Perylene Diimide Amorphous Films
