Synthesis and photovoltaic characterization of triarylamine-substituted quinoxaline push--pull dyes to improve the performance of dye-sensitized solar cells

Novel unsymmetrical organic sensitizers having donor, $\pi $-spacer, and anchoring groups were designed and synthesized for dye-sensitized solar cell (DSSC) application. The dyes 3-{4-[7-(4-{bis[4-(hexyl)phenyl]amino} phenyl)-11,12-dibutoxy-1,4,5,8-tetrahydrodibenzo [a, c] phenazine-2-yl]phenyl} -2-cyano acrylic acid (KD-148) and 3-{5-[7-(4-{bis[4-(hexyloxy)phenyl]amino} phenyl)-11,12-dibutoxy-1,4,5,8-tetrahydrodibenzo [a, c] phenazine-2-yl]-2-thienyl} -2-cyano acrylic acid (KD-150) were anchored onto TiO$_{2}$ and tested with ionic liquid electrolyte. The monochromatic incident photon-to-current conversion efficiencies (IPCE) of the dyes were 50% and 60% at 420 nm, respectively. The KD-150-sensitized solar cell gave a short-circuit current (I$_{SC})$ of 7.37 mA/cm$^{2}$, an open-circuit voltage (V$_{oc})$ of 560 mV, a fill factor (FF) of 0.56, and overall conversion efficiency ($\eta )$ of 2.32% whereas the standard dye Z-907 dye exhibited 14.51 mA/cm$^{2}$ of I$_{SC}$, 630 mV of V$_{oc}$, 0.45 of FF, and 4.08% of $\eta $ under AM 1.5 illumination with power of 100 mW/cm$^{2}$.