The Theoretical Investigation On Co-sensitization Mechanism In Dye-sensitized Solar Cells

By means of the density functional theory (DFT) and the time dependent densityfunctional theory (DT-DFT), individual donor-π-acceptor organic dyes, which havecomplementary optical properties, denoted as C239, C259and C259-N were designedtheoretically as co-sensitizers for dye-sensitized solar cells. Optical and electronicproperties of the co-sensitized dyes were investigated and the main results are shown asfollows:The co-sensitizers can show broad spectral response in visible region (300-800nm) andthe light-harvesting efficiency over the entire visible region is improved compared withindividual dyes. Butthe excitations of co-sensitized C239+C259/C259-Nat300-400nmwere observed to be inefficient in charge transfer, where a lower IPCE value may exist.In“b” co-sensitization mode, the absorption spectra become broader and theλmaxis red-shift,but in “a” co-sensitization mode, it has a blue-shift forλmax.Also, the strength of absorptionbands in “b” mode is more intense than that in “a” mode. So the co-sensitizers in “b” modecanimprove the efficiency of theDye-sensitized solar cells.This study is helpful for further understanding about how the co-sensitized dyes affectthe performance of a cell.And the results can supply a guide forexperimentto further designmore effective solar cells.