Recently, the performance of ZnO nanocrystals as an electron acceptor in a solar cell device was significantly increased by a semiconducting surfactant. Here we show, using transient absorption spectroscopy and a parallel pool analysis, that changes in the quantum efficiency of charge generation account for the performance variation among semiconducting-surfactant-coated, surfactant-coated, and uncoated ZnO nanoparticles. We demonstrate that even better surfactant design to suppress fast recombination could still lead to a further doubling of device efficiency.