How Mixing Different Components Contributes to the Reduction of Crystal Growth Rate

The influence of thermodynamic and kinetic factors on the crystal growth rate reduction upon mixing 4,7-diphenyl-1,10-phenanthroline (BPhen) and hydroxyquinolinolato-lithium (Liq) molecules was investigated. Mixing Liq above 17 vol % mostly prevents crystallization, while a reduced crystal growth rate was observed between 0 and 15 vol % Liq. When mixed films were crystallized, only BPhen was crystallized, and the temperature dependence of crystal growth rate followed the 2D growth mechanism. The narrowed temperature gap between the glass transition and melting temperatures, along with the decreased enthalpy of fusion, slows the crystal growth rate by adjusting both kinetic and thermodynamic aspects. Additionally, mixing steepens the temperature dependence of molecular mobility, further decreasing the crystal growth rate in the kinetically controlled region. Conversely, it decreases interfacial energy, which impedes the crystal growth rate reduction caused by the narrowing of the temperature gap in the thermodynamically controlled region.