Insights into the β‐phase of polyfluorene: characterization, regulation, and mechanism

Abstract

Due to the unique blue‐light properties, wide excited emission interval and so on, polyfluorenes (PFs) are among the most promising blue‐light polymers that are widely used in organic lasers and organic light‐emitting diodes. Usually, PFs exhibit two different phases: α‐phase and β‐phase, and the β‐phase has higher photoluminescence efficiency and carrier mobility than the one of α‐phase. Hence, improving the content of β‐phase is very important to enhance the device performance. In this paper, we introduce the methods for characterizing the β‐phase in PFs and summarize the recent research progress in regulating the β‐phase content. Firstly, the differences between the α‐phase and the β‐phase of PFs in terms of structure, aggregation behavior, and optoelectronic properties are summarized. Then, the characterization for the β‐phase, including ultraviolet–visible absorption spectrum (UV–vis), photoluminescence spectrum (PL), and Raman spectrum, transmission electron microscope (TEM), and X‐ray diffraction (XRD) are introduced, and the calculating rules for the content of β‐phase is also introduced. Furthermore, the methods to increase the content of β‐phase are reviewed. Finally, a brief outlook on the challenges and future development prospects of β‐phase in PFs are discussed.