DFT/TDDFT and Experimental Studies of Natural Pigments Extracted from Black Tea Waste for DSSC Application

Table 3

DFT and TDDFT calculations of four theaflavin analogues with inclusion of solvation effect of ethanol.

Tea polyphenol	DFT calculation			TDDFT calculation (excitation state 𝑛=3)
	HOMO	LUMO	Band gap	Calculated energy		Oscillator strength	MO (coefficient)*
	(eV)	(eV)	(eV)	(eV)	(nm)	(f)
TF	−5.32	−2.18	3.13	2.71	458	0.1005	H→L=0.675
				2.99	415	0.1754	H→L+1=0.667
				3.13	396	0.0001	H-1→L=0.703
T3G	−5.61	−2.08	3.52	2.83	439	0.0666	H→L=0.696
				3.34	372	0.0005	H-1→L=0.692
				3.42	363	0.0002	H-2→L=0.635
T3′G	−5.73	−2.21	3.52	2.82	440	0.0502	H→L=0.669
				3.18	390	0.0002	H-1→L=0.672
				3.31	374	0.0012	H-2→L=0.682
TDG	−5.38	−2.23	3.15	2.69	461	0.0908	H→L=0.683
				3.03	409	0.1937	H→L+1=0.672
				3.16	393	0.0008	H-1→L=0.700

∗Molecular orbital with coefficient less than 0.2 is not shown.