The effects of post-growth annealing on the structure, morphology, and spectroscopic properties of molecular double-layer heterostructures containing perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and metal-free phthalocyanine (H2PC) have been investigated. The templated structure adopted by H2PC on PTCDA protects the underlying PTCDA layer from sublimation, unless the H2PC thickness is < 20 nm (see Figure).