Abstract
The sensitizer is one of the key components in achieving the high efficiency and durability of a dye-sensitized solar cell (DSSC) device. The porphyrin class of sensitizers using the donor-[Formula: see text]-acceptor concept with either I[Formula: see text]/I[Formula: see text] or Co(II/III) redox couples have demonstrated device efficiency >10%. The sensitizer with triphenylimidazole donor and and 3-(5(benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2yl)-2-cyanoacrylic acid as an acceptor (LG18) have illustrated device efficiency of 10.51%. In this report, we adopted femtosecond transient absorption (fs-TA) spectroscopy to explore the ensuing relaxation properties of LG18 and adsorbed on TiO2 in solution upon 400 nm photoexcitation. Comparative analysis of the obtained TA data matrices of LG18 and LG18–TiO2 samples confirms an ultrafast hot electron extraction (<150 fs, >k[Formula: see text] = 6.5 × 10[Formula: see text] s[Formula: see text] along with multi-step electron injection occurs from different excited states of LG18 with rate constant (k[Formula: see text] in the range of 6.7 × 10[Formula: see text] s[Formula: see text] to 5 × 108 s[Formula: see text] which are 3-4 order higher than charge recombination rate (k[Formula: see text] [Formula: see text]<1 × 108 s[Formula: see text].
Published Version
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