Strategic Synchronization of 7,7-Dimethyl-5,7-dihydroindeno[2,1-<i>b</i>]carbazole for Narrow-Band, Pure Violet Organic Light-Emitting Diodes with an Efficiency of &gt; 5% and a CIE <i>y</i> Coordinate of &lt; 0.03

Abstract

A novel violet emitter, 1,3-bis[10,10-dimethyl-10<i>H</i>-indeno[2,1-<i>b</i>]]indolo[3,2,1-<i>jk</i>]indolo[1',2',3':1,7]indolo[3,2-<i>b</i>]carbazole (<i><b>m</b></i><b>-FLDID</b>), was designed and synthesized by <i>meta</i>-oriented <i>bis</i>-fusion of two 7,7-dimethyl-5,7-dihydroindeno[2,1-<i>b</i>]carbazole (<b>DMID</b>) subunits for use in a pure violet organic light-emitting diode (OLED). Incorporation of the <b>DMID</b> subunits effectively reduced the nonradiative recombination rate, improving the photoluminescence quantum yield of the <i><b>m</b></i><b>-FLDID</b> emitter. The <i>meta</i>-oriented <i>bis</i>-fusion of the two <b>DMID</b> subunits not only triggered an alternative distribution of the frontier orbitals but also effectively locked the π-conjugation chain, which ultimately resulted in a narrow-band, pure violet emission of the <i><b>m</b></i><b>-FLDID</b> emitter. Doped <i><b>m</b></i><b>-FLDID</b> devices possessed an external quantum efficiency (EQE) of > 5%, pure violet emission with a maximum at 407 nm, a narrow full width at half-maximum of 17 nm, and a <i>Commission Internationale de l'éclairage</i> <i>y</i> coordinate of less than 0.03. This is the first work reporting an EQE of > 5% and an extremely narrow emission spectrum for a pure violet emitter.