CuIn_0.7Ga_0.3S₂ quantum dots (QDs) with particle size of 2–5 nm were directly synthesised by a vacuum one-pot-nanocasting process and homogeneously anchored on TiO₂ nanocrystals (<50 nm) for the first time. We further present CuIn_0.7Ga_0.3S₂ quantum dots and dye bilayer-sensitized solar cells with a power conversion efficiency 36.3% higher than mono-dye sensitized solar cells.