REAL-TIME VISUALIZATION OF MORPHOLOGICAL EVOLUTION OF N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine THIN FILMS: VARIABLE TEMPERATURE ATOMIC FORCE MICROSCOPY STUDY

Abstract

Variable temperature tapping mode atomic force microscopy is exploited to in situ visualize the morphological evolution of N, N'-di(naphthalene-1-yl)-N, N'-diphthalbenzidine (NPB) thin film. The apparent glass transition of the NPB thin film initially occurred at 60°C, proceeded until 95°C, and crystallization from the glassy state quickly appeared at 135°C. The NPB thin film gradually melted and disappeared when the temperature was above 175°C, revealing the underlying layer. These observations are technically helpful and significant to gauge the temperature dependent lifetime and luminance of organic light-emitting diodes.