A squaraine dye as molecular sensitizer for increasing light harvesting in polymer solar cells

In this work, a near-infrared (NIR) absorbing squaraine dye, 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ), was added as a molecular sensitizer into poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) polymer solar cells to improve their power conversion efficiency (PCE). The absorption of the additional DIBSQ contributed to the photoresponse of the cells in the NIR region. The enhancement of light harvesting efficiently increased the short-circuit current density, and thus improved the PCE by ∼10%. The optimized PCE of 3.4% under 1 sun, AM 1.5G solar irradiation was achieved with the DIBSQ:P3HT:PCBM system that included 3 or 5 wt% of DIBSQ. Our results show that DIBSQ is a promising molecular sensitizer for increasing the PCE of P3HT:PCBM polymer solar cells.