For efficient charge separation and charge transport in optoelectronic materials,
small internal reorganization energies are desired. While many p-type organic
semiconductors have been reported with low internal reorganization energies, few
n-type materials with low reorganization energy are known. Metal phthalocyanines
have long received extensive research attention in the field of organic device
electronics due to their highly tunable electronic properties through
modification of the molecular periphery. In this study, density functional
theory (DFT) calculations are performed on a series of zinc-phthalocyanines
(ZnPc) with various degrees of peripheral per-fluoroalkyl
(-C3F7) modification. Introduction of the highly electron
withdrawing groups on the periphery leads to a lowering in the energy of the
molecular frontier orbitals as well as an increase in the electron affinity.
Additionally, all molecules studies are found to be most stable in their anionic
form, demonstrating their potential as n-type materials. However, the calculated
internal reorganization energy slightly increases as a function of peripheral
modification. By varying the degree of modification we develop a strategy for
obtaining an optimal balance between low reorganization energy and high electron
affinity for the development of novel n-type optoelectronic materials.