Perylene Dyes

　Perylene was a p-type organic semiconductor and it was known in the 1950s that the bromine-doped material showed electrical conductivity.¹⁾ In contrast to that, perylenetetracarboxylic dianhydride and perylenetetracarboxylic diimide derivatives are n-type organic semiconductors. The latter perylenetetracarboxylic derivatives (PDI or PBI) are important semiconducting materials, because n-type ones are relatively less known than p-type ones. In fact, PTCBI (3,4,9,10-perylenetetracarboxylic bisbenzimidazole) was an n-type organic semiconductor for a prototype of organic photovoltaics.²⁾
　Applications in organic electronics using PDI derivatives are organic light-emitting diode (OLED) materials³⁾ and laser dyes⁴⁾ thanks to their high fluorescent quantum efficiency and photochemical stability. PDIs with electron mobility larger than 0.1 cm²/Vs are also reported.^5,6) An introduction of an alkyl group on the imido moiety (NR) produces soluble PDI derivatives, although they are poorly soluble in general.⁷⁾ Recent research has proved direct alkylations at the meta positions (1,6,7,12-positions),^8,9) and direct boronations at the ortho positions (2,5,8,11-positions)¹⁰⁾ for PDIs. Halogenations at the meta positions are available, followed by various cross-coupling reactions¹¹⁾ and polymerizations¹²⁾ providing PDI derivatives with diverse molecular structures and molecular weights.