Dye-sensitized solar cells prepared using nanoparticle pastes typically require high annealing temperature to eliminate organic binders and achieve good performance. Here we show that for ZnO nanoparticle based solar cells, optimal annealing temperature is strongly dependent on the properties of ZnO nanoparticles. For ZnO nanoparticles with low native defect concentrations, significantly higher power conversion efficiencies are obtained for a low annealing temperature of 150 degrees C compared to commonly used annealing temperature of 450 degrees C (20-40% increase, depending on the starting particle properties). (C) 2015 Elsevier B.V. All rights reserved.