Tuning the Liquid Crystallinity and Electroluminescence via Sulfonation of S‐Annulated Perylene Tetraester

This study presents a comparative analysis of S‐annulated perylene tetraester (PTE‐S) and its sulfone (PTE‐SO2) analogue. This sulfone modification reduced melting point and stabilized a room temperature columnar rectangular (Colr) phase in contrast to its parent PTE‐S which showed a crystalline behaviour at room temperature. This molecular design also leads to red‐shifted absorbance and emission in comparison to PTE‐S, along with a tuning of photoluminescence from sky blue to green, achieving an impressive quantum yield of 85 %. OLED devices fabricated using PTE‐SO2 as emitter material at concentrations of 0.2, 0.5, and 1 wt.% in CBP as host material. A maximum external quantum efficiency (EQE) of 2.9 % was observed with the 0.5 wt.% PTE‐SO2 in CBP with CIE coordinates of (0.45, 0.35), accompanied by an orange luminance of 848 cd/m2. Notably, a device with a 0.5 wt% doping concentration of PTE‐S demonstrates an EQE of 3.5 %, and cyan luminance of 2,598 cd/m2. Tuning of liquid crystallinity, fluorescence and electroluminescence by molecular design.