Diarylfluorene-Based Organic Semiconductor Materials toward Optoelectronic Applications

Modular production is a convenient strategy that not only realizes the mass production of conjugated materials, but also precisely regulates their photoelectrical property for optoelectronic applications. Diarylfluorene is a functional building block in constructing organic semiconductors arising from its special electronic, spacial, and conformational structure. Because of easy chemical modification, tunable electronic structure, and high photoluminescence quantum yield, diarylfluorene-based conjugated materials have undergone remarkable development in variety of low-cost optoelectronic devices. Herein, the authors present an overview mainly to describe the recent research progresses of diarylfluorene-based molecules, including 9,9′-diarylfluorene, heteroatom-containing spirocyclic diarylfluorene, and 4-position substituted 9,9′-diarylfluorene. The synthetic routes, molecular structures as well as their diverse applications toward optoelectronic devices are introduced and summarized systematically. Finally, the future challenges and development are also discussed in this vital research field.     

Flexible Metal‐Free Memory Electronic Made of π‐Conjugation‐Interrupted Hyperbranched Polymer Switch and Reduced Graphene Oxide Electrodes

A flexible metal‐free flash memory device with reduced graphene oxide films as electrodes and diarylfluorene‐based π‐conjugation‐interrupted hyperbranched polymers (CIHPs) as active switches is reported. Two CIHPs, named PCzPF and PCzPF‐PF, are synthesized via BF₃?Et₂O‐catalyzed fluorenol’s Friedel–Crafts reaction, where the PCzPF‐PF is designed by the decoration of hindrance functional groups, i.e., bulky 9‐phenyl‐fluorenyl (PF) moieties, at the end‐groups of PCzPF. Both of the two CIHPs exhibit excellent solubility and thermal stability. The PCzPF‐based device exhibits no switching effect while the PCzPF‐PF‐based device shows a flash type memory effect, indicating the incorporation of PF groups plays a critical role in realizing electrically bistable behaviors. In particular, the optimized memory exhibits a high ON/OFF ratio of > 3.0 × 10³, long retention time of up to 1.2 × 10⁴ s, and high mechanical stability. This work opens a new avenue for metal‐free memory electronics through a low‐cost and full‐solution process approach.