Quantum-Dot-Based Light-Emitting Diodes With Improved Brightness and Stability by Using Sulfuric Acid-Treated PEDOT:PSS as Efficient Hole Injection Layer

Spin-coated poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) thin film was treated with H ₂ SO ₄ and used as hole injection layer in quantum-dot-based lightemitting diodes (QD-LEDs). Such QD-LEDs with a H ₂ SO ₄ -treated PEDOT:PSS layer demonstrate improved carrier injection efficiency and luminance. Especially, the electroluminescence stability was greatly improved as well. Nearly 72% of peak luminance of QD-LEDs was preserved even after 24 h exposure in air for devices using H ₂ SO ₄ -treated PEDOT:PSS film, while a rapid loss of 98% of peak luminance within a day for untreated devices was recorded. The improved performance for QD-LEDs with H ₂ SO ₄ -treated PEDOT:PSS film probably originated from the conformational change of the polymer chains and the removing of the insulating and hydrophilic PSSbases from PEDOT:PSS layer. Such a simple but effective process may provide beneficial references for the development of high performance and long stability thin-film LEDs.