Efficient near IR porphyrins containing triphenylamine substituted anthryl donating group for dye sensitized solar cells
Three porphyrin dyes comprising of 4-(10-ethynylanthracen-9-yl)-N,N-diphenylaniline as extended π-conjugated donor integrated with systematic variation of acceptor groups i.e., 2-cyano-3-(5-methylthiophen-2-yl)acrylic acid (LG19), 2-cyano-3-(5-(7-methylbenzo[c][1,2,5] thiadiazol-4-yl) thiophen-2-yl)acrylic acid (LG20), and 2-cyano-3-(4-(7-methyl benzo[c][1,2,5] thiadiazol-4-yl) phenyl)acrylic acid (LG21) has been synthesized and implemented in dye sensitized solar cells (DSSCs). All these sensitizers were characterized by various spectroscopic and electrochemical techniques. The absorption maxima of LG20 significantly red-shifted to 707 nm, when compared to LG19 and LG21 sensitizers. Optical, electrochemical and theoretical studies suggest that the lowest unoccupied molecular orbital (LUMO) of LG20 and LG21 are very close to TiO2 conduction band, when compared to LG19. The IPCE of LG20 and LG21 found to be 81% at 486 nm and 83% at 482 nm, respectively and the onset wavelengths were shifted up to 900-980 nm. With favourable red-shifted absorption of LG20 sensitizer, a high power conversion efficiency (PCE) of 10.0% has been observed for the fabricated DSSC which was higher than the DSSCs fabricated by LG19 (PCE=8.51%) and LG21 (PCE=9.04%). Therefore, the effect of extended π-conjugated donor, anchoring group, benzothiadiazole auxiliary acceptor and presence of dodecyloxy groups singnificantly contributed in enhancing the efficiency of the device using liquid redox electrolyte. Finally, we have used intensity modulated photovoltage spectroscopy and nanosecond transient studies to explaing the design and efficiency relationship of these sensitizers.