Understanding the thermal-annealing-generated stable structure of phthalocyanine derivative/polymer bicomponent systems through scanning tunneling microscopy and density functional theory calculations

Understanding the formation of stable surface structures of organic bicomponent systems during thermal annealing is highly desired in the current developments of efficient photoelectronic devices and molecular electronics. In this work, evolution of surface structures of phthalocyanine derivative/polymer bicomponent systems during thermal annealing was investigated at molecular level through scanning tunneling microscopy, density functional theory (DFT) calculations and molecular dynamics simulations. The results of fully fluorinated copper phthalocyanine (F16CuPc)/PffBT4T (polymer 1)/graphite (G) suggest that the most stable surface assembly produced by thermal annealing corresponds to the structure with lowest energy in DFT calculations. This finding was verified further in both F8H8CuPc/PffBT4T/G and H16CuPc/PffBT4T/G systems. With this testified finding, the annealing-generated stable arrangements of F16CuPc/PQT (polymer 2)/G, F8H8CuPc/PQT/G and H16CuPc/PQT/G are successfully predicted. Thus, our study reveals that the structure with lowest energy is an essential parameter for understanding or predicting thermal-annealing-generated stable surface structures of bicomponent systems.