The use of energy relay dyes in dye sensitized solar cells presents an opportunity to improve efficiency by increasing the range of absorption of the solar spectrum. In experiments, relay dyes have achieved high efficiency of energy transfer to the sensitizing dye, but the overall power conversion efficiencies of the solar cells is not yet competitive with single-dye dye sensitized solar cells. Using kinetic Monte Carlo simulations, we explored how energy transfer among relay dyes affects the energy transfer to sensitizing dyes and found that high concentrations of energy relay dyes with high rates of homotransfer (a large donor-to-donor Forster radius) can be used to improve the efficiency of excitation transfer to the sensitizing dyes. We examined the effect of Forster radii, quenching, pore size, and dye concentration on the excitation transfer efficiency. The improved understanding of the interplay between the donor–donor and donor–acceptor Forster transfer radii effectively relaxes requirements and e...