This paper describes the solution preparation of thin films composed of quantum dots and thiacyanine J-aggregates, making use of the size tunable emission of quantum dots and the narrow, intense absorption of J-aggregates in the solid state. These blended films exhibit 90% energy transfer efficiency from J-aggregates to quantum dots and can uniformly cover a large area. Because the presence of the J-aggregates enhances the QD photoluminescence intensity by 2.5-fold over QDs alone, these solid state materials may be useful in downconversion applications or in fundamental investigations of light harvesting.