Dye-sensitized bulk heterojunction polymer solar cells

At present, there is a real limitation one can achieve with state-of-the-art fullerene-polymer solar cell materials in a fully optimized device based upon the poor mismatch to the solar spectrum. Empirical modeling has been performed using device parameters from current-voltage and spectral response measurements. The limiting Jsc has been simulated from the spectral response profile of PCBM[70]-MEH-PPV and PCBM[60]-P3HT devices. The maximum efficiency for these systems is calculated to be between 6 and 9%, under 1 sun illumination. Empirical simulations show that molecular dyes absorbing between 800-900 nm in a properly structured device can theoretically increase the device photocurrent sufficient to reach a power conversion efficiency of 16% in a bulk heterojunction polymer solar cell under 1 sun AM1.5 illumination. We have investigated the use of soluble organic dyes with measured bandgaps in the nearinfrared (NIR) to extend the spectral conversion in polymeric solar cells. An appropriate energy level structure (to promote exciton dissociation and charge transport to the fullerene derivatives and polymer) has been measured using cyclic voltammetry for certain indolylidene dyes. The incorporation of these dyes into a PCBM-P3HT device structure has shown an enhancement in the spectral response at 1.5 eV.