Insight into the effects of modifying chromophores on the performance of quinoline-based dye-sensitized solar cells

A series of organic dyes based on quinoline as an electron-deficient π-linker, were designed and synthesized for dye sensitized solar cells (DSSC) application. These push-pull conjugated dyes, sharing same anchoring group with distinctive electron-rich donating groups such as N,N-diethyl (DEA-Q), 3,6-dimethoxy carbazole (CBZ-Q), bis(4-butoxyphenyl)amine (BPA-Q), were synthesized by Riley oxidation of CH₃ followed by Knoevenagel condensation of the corresponding aldehyde precursors 2a-c with cyanoacrylic acid. The optical, electrochemical, theoretical calculation and photovoltaic properties with these three dyes were systematically investigated. Compared to DEA-Q and CBZ-Q, BPA-Q possesses better light harvesting properties with regard to extended conjugate length, red-shifted intramolecular charge transfer band absorption and broaden light-responsive IPCE spectrum, resulting in a greater short circuit photocurrent density output. BPA-Q also has improved open-circuit voltage due to the apparent large charge recombination resistance. Consequently, assembled with iodine redox electrolytes, the device with BPA-Q achieved the best overall conversion efficiency value of 3.07% among three dyes under AM 1.5G standard conditions. This present investigation demonstrates the importance of various N-substituent chromophores in the prevalent D-π-A type organic sensitizers for tuning the photovoltaic performance of their DSSCs.