Multichromophoric energy sensitization of C60 for organic photovoltaics

In organic photovoltaics (OPVs), photocurrent generation is limited by absorption and exciton diffusion in the active layer. In this work, we describe the energy sensitization of C-60 simultaneously by two chromophores at high volume concentrations (50%). This sensitization strategy takes advantage of the intense absorption of the sensitizers and the exceptional electron conduction and exciton diffusion length of C-60 resulting in a 30% increase in photoresponse of the C-60-based sensitized acceptor layer between lambda = 450 nm and 670 nm and power conversion efficiency under simulated AM 1.5G illumination. In (2,4-bis[4-(N, N-diphenylamino)-2,6-dihydroxyphenyl] squaraine)/C-60 devices, sensitization results in an increase in J(SC) from 6.5 +/- 0.2 mA/cm(2) to 8.6 +/- 0.2 mA/cm(2) without compromising V-OC or FF. These results demonstrate the robust nature of this sensitization scheme and its broad potential for application in OPVs. (C) 2014 AIP Publishing LLC.