Highly Efficient Rigidified Quinoxaline-based Co-Sensitizers Carrying Long Alkyl Chains for Ruthenium-Complex-Sensitized DSSCs

In this paper, cosensitized DSSCs(Dye-Sensitized Solar Cell) using quinoxaline-based co-sensitizers along with a well-known ruthenium dye were fabricated, and their photophysical properties and photovoltaic characteristics were measured to comprehensively assess the effect of molecular architecture on the photovoltaic performance of devices. We revealed the key role of bulky rigid quinoxaline-based co-sensitizers in enhancing the overall efficiency of DSSCs for the first time. From the results, it is evident that the co-sensitizer exhibited excellent performance in improving the photocurrent of cosensitized DSSCs. The cell cosensitized with 0.2 mm of quinoxaline-based co-sensitizer and 0.2 mm of ruthenium dye, exhibited the highest efficiency of 7.88 % (J(SC)=20.82 mA cm(-2), V-OC=0.614 V, FF=61.6 %) when compared to ruthenium dye alone. Smaller organic co-sensitizers cannot make up for the weak absorption in the range of about 350-600 nm of ruthenium dyes, but also filled up the space between the bulky ruthenium dye molecules, leading to more effective coverage on the TiO2 surface. Hence, it was observed that the FF(Fill Factor) values were improved for all the cells. Thus, based on the above-mentioned results, quinoxaline-based co-sensitizer showed good potential in enhancing photovoltaic efficiency of DSSCs at the appropriate concentration.

Automated summary

This paper fabricated cosensitized DSSCs using quinoxaline-based co-sensitizers and a ruthenium dye, and comprehensively assessed the effect of molecular architecture on the photovoltaic performance of devices. The results showed that bulky rigid quinoxaline-based co-sensitizers played a key role in enhancing the overall efficiency of DSSCs.