Aromatic S-Heterocycle and Fluorene Derivatives as Solution-Processed Blue Fluorescent Emitters: Structure–Property Relationships for Different Sulfur Oxidation States

Abstract

Based on the two systems of dibenzothiophene (DBT) and phenothiazine (PTZ), blue fluorescent small molecules (D1 and D2, P1 and P2) constructed of aromatic S-heterocycles with different sulfur oxidation states (sulfides or sulfones) were synthesized. The property discrepancies caused by the difference of sulfur oxidation states were investigated, including that of thermal stability, photophysical property, electrochemistry behavior, carrier transport property, and electroluminescence performance. Higher sulfur oxidation states induced significantly better electron-injection and transport abilities, which is potentially beneficial to enhance the performance of solution-processed (SP) small-molecule (SM) devices. Single-layer SP OLEDs with the structures of ITO/PEDOT:PSS (40 nm)/emitters (80 nm)/CsF (1.5 nm)/Al (120 nm) were fabricated. The DBT system exhibited high electroluminescence performances with a maximum external quantum efficiency of 1.7% (D1) and 2.6% (D2), respectively, which are among the best ...