310
K. Tanaka et al.
emission can be observed in the aggregation state. Furthermore, it was shown that
emission color from some of the AIE-active molecules was sensitive to molecular
distributions in the solid state. Based on these characteristics, stimuli-responsive
luminochromism was obtained. Basic design strategies and recent applications are
described.
Keywords Boron · Carborane · Solid-state luminescence · Luminochromism ·
Element-block · Aggregation-induced emission
9.1 Introduction
Organic luminescent dyes are versatile for developing advanced optoelectronic
devices because of their property tunability according to preprogrammed designs
and intrinsic superior material properties to inorganics, such as lightness, solubility,
compatibility in various media, and processability. Therefore, not only electroluminescent panels but also flexible displays have been developed based on organic materials, and some of them have been already commercialized. Meanwhile, in common
devices, luminescent dyes are used as a film. Therefore, efficient solid-state luminescence is the essential requirement to obtain practical products. However, most
of the organic dyes show critical decreases in their emission characteristics in the
condensed state by non-specific intermolecular interactions in the ground and/or
excited states even though intense emission can be observed in the diluted solution. This phenomenon is called as concentration quenching or aggregation-caused
quenching (ACQ).
In this chapter, the design strategies for obtaining solid-state luminescence from
on organic optical materials and particularly boron-containing dyes, as an example,
are described. So far, there are several strategies for obtaining efficient solid-state
emission as shown in reviews (Anthony 2012; Shaikh et al. 2015; Carayon and
Fery-Forgues 2017; Varughese 2014; Xue et al. 2016; Shimizu and Hiyama 2010).
By introducing twisting structures (Zhu et al. 2018; Wang et al. 2018; Srujana and
Radhakrishnan 2018; Takayanagi et al. 2018; Xu et al. 2018; Zhu et al. 2018; Yu et al.
2017) or heteroatom units (Namba et al. 2018; Shimizu et al. 2017; Munch et al. 2019;
Shao et al. 2019; Sun et al. 2018; Jia and Wu 2017) in the conjugation system, ACQ
is able to be suppressed. Intermolecular interaction can be disturbed by introducing
bulky substituents directly into molecular structures to some extent (Sun et al. 2019;
Yan et al. 2017; Iida and Yamaguchi 2009; Hariharan et al. 2017; Huang et al. 2018;
Peng et al. 2019; Gu et al. 2017; Hirosawa et al. 2017). This strategy is also applicable for obtaining luminescent polymers having extended π-conjugation through
main chains. In particular, the boron-containing units have been utilized as a versatile
platform not only for obtaining intense luminescence but also for suppressing ACQ
(Zhao et al. 2006; Wang et al. 2015; Ohsedo et al. 2015; Yan et al. 2014; Wakamiya
et al. 2007; Shimizu et al. 2015; Kalluvettukuzhy and Thilagar 2017; Zhang et al.
2018; Zhao et al. 2007); Nie et al. 2019; Weber et al. 2012). In this chapter, initially,
K. Tanaka et al.
emission can be observed in the aggregation state. Furthermore, it was shown that
emission color from some of the AIE-active molecules was sensitive to molecular
distributions in the solid state. Based on these characteristics, stimuli-responsive
luminochromism was obtained. Basic design strategies and recent applications are
described.
Keywords Boron · Carborane · Solid-state luminescence · Luminochromism ·
Element-block · Aggregation-induced emission
9.1 Introduction
Organic luminescent dyes are versatile for developing advanced optoelectronic
devices because of their property tunability according to preprogrammed designs
and intrinsic superior material properties to inorganics, such as lightness, solubility,
compatibility in various media, and processability. Therefore, not only electroluminescent panels but also flexible displays have been developed based on organic materials, and some of them have been already commercialized. Meanwhile, in common
devices, luminescent dyes are used as a film. Therefore, efficient solid-state luminescence is the essential requirement to obtain practical products. However, most
of the organic dyes show critical decreases in their emission characteristics in the
condensed state by non-specific intermolecular interactions in the ground and/or
excited states even though intense emission can be observed in the diluted solution. This phenomenon is called as concentration quenching or aggregation-caused
quenching (ACQ).
In this chapter, the design strategies for obtaining solid-state luminescence from
on organic optical materials and particularly boron-containing dyes, as an example,
are described. So far, there are several strategies for obtaining efficient solid-state
emission as shown in reviews (Anthony 2012; Shaikh et al. 2015; Carayon and
Fery-Forgues 2017; Varughese 2014; Xue et al. 2016; Shimizu and Hiyama 2010).
By introducing twisting structures (Zhu et al. 2018; Wang et al. 2018; Srujana and
Radhakrishnan 2018; Takayanagi et al. 2018; Xu et al. 2018; Zhu et al. 2018; Yu et al.
2017) or heteroatom units (Namba et al. 2018; Shimizu et al. 2017; Munch et al. 2019;
Shao et al. 2019; Sun et al. 2018; Jia and Wu 2017) in the conjugation system, ACQ
is able to be suppressed. Intermolecular interaction can be disturbed by introducing
bulky substituents directly into molecular structures to some extent (Sun et al. 2019;
Yan et al. 2017; Iida and Yamaguchi 2009; Hariharan et al. 2017; Huang et al. 2018;
Peng et al. 2019; Gu et al. 2017; Hirosawa et al. 2017). This strategy is also applicable for obtaining luminescent polymers having extended π-conjugation through
main chains. In particular, the boron-containing units have been utilized as a versatile
platform not only for obtaining intense luminescence but also for suppressing ACQ
(Zhao et al. 2006; Wang et al. 2015; Ohsedo et al. 2015; Yan et al. 2014; Wakamiya
et al. 2007; Shimizu et al. 2015; Kalluvettukuzhy and Thilagar 2017; Zhang et al.
2018; Zhao et al. 2007); Nie et al. 2019; Weber et al. 2012). In this chapter, initially,