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 (F 16 CuPc)/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 F 8 H 8 CuPc/PffBT4T/G and H 16 CuPc/PffBT4T/G systems. With this testified finding, the annealing-generated stable arrangements of F 16 CuPc/PQT (polymer 2)/G, F 8 H 8 CuPc/PQT/G and H 16 CuPc/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. • Annealing processes of F x H 16-x CuPc/PffBT4T/G were studied by STM and DFT. • The link between the stable surface assembly and lowest energy structure was built. • With the above findings, stable arrangements of F x H 16-x CuPc/PQT/G are predicted. • Key role of the lowest-energy structure in rationalizing structural evolution.