Solution-processable hole-transporting materials for organic light-emitting diodes

Hole-transporting materials (HTMs) are critical components of organic light-emitting diodes (OLEDs). A large number of solution-processable HTMs have been achieved with rapid development in the area of OLEDs in the last couple of decades. It is pivotal to systematically explore the structure–property-stability of the solution-processed HTM for enhancing the device performances towards low-cost and large-area mass production. Rational molecular designs of HTMs are essential and inevitable since the hole transport ability and morphological engineering in the condensed phases govern these optoelectronic processes. In this chapter, we focus on discussing the development of molecular design principles of the solution-processable HTMs. In contrast to the contents involved in other chapters, the structural segments and topological structures of HTMs are emphasized here to explain their charge transporting property, solubility, morphological stability, and applications in solution-processed OLEDs. Similar to the industrial Lego, the key segments presented in this chapter will provide an effective platform to realize the rational design and modular production of the solution-processed HTMs for manufacturing efficient and stable OLEDs.