Near-infrared unsymmetrical squaraine core-based sensitizers for co-sensitized high-photocurrent dye-sensitized solar cells

Increased conversion of near-infrared (NIR) photons to electricity is needed to improve dye-sensitized solar cells (DSCs). Here, we report two squaraine dyes (RR13 and RR14) with unsymmetrical cores as NIR dyes in DSCs. Both dyes feature a conjugated indolizine donor with an indoline donor on the opposite side of the squaraine core. The dyes are studied via absorption spectroscopy, computational interrogation, and electrochemical analysis. The use of the strongly donating indolizine donor results in NIR photon-to-current conversion extending beyond 800 nm on TiO2 in DSC devices. The DSC devices were characterized by current-voltage curves, incident photon-to-current conversion efficiency measurements, and electrical impedance spectroscopy. After co-sensitized DSC device optimizations, the NIR-absorbing squaraine dyes complemented with commercial organic dyes (D35 and Y123) gave a high photocurrent output of similar to 21 mA/cm(2) with a PCE of 9.4%.

Automated summary

This study reports two squaraine dyes with unsymmetrical cores as near-infrared dyes in dye-sensitized solar cells (DSCs). The dyes were characterized through absorption spectroscopy, computational interrogation, and electrochemical analysis. After optimizing the DSC devices, the squaraine dyes showed high photocurrent output and conversion efficiency, complemented with commercial organic dyes.