All-solution Processed High Performance Inverted Quantum Dot Light Emitting Diodes
All-solution processed colloidal quantum dot light emitting diodes (QLEDs) with record performance have been successfully realized by introducing dually-doped poly(ethylenedioxythiophene)/polystyrenesulfonate (PEDOT:PSS) hole-injection layer and polyethylenimine (PEI) interfacial layer. Doping PEDOT:PSS with both Zonyl and isopropanol (IPA) significantly improves the wettability of PEDOT:PSS, making coating hydrophilic PEDOT:PSS onto hydrophobic hole-transporting layer poly(9-vinlycarbazole) (PVK) possible. The PEI interlayer between PVK/QD layer not only lowers down the vacuum level, thereby reducing the hole-injection barrier to balance the charge carriers, but also passivates QD surface defects via its amine group to suppress fluorescence quenching. As a result, the peak current efficiency of 28.1 cd/A, 43.1 cd/A, and 1.26 cd/A, the maximum external quantum efficiency (EQE) of 20.6%, 10.4%, and 2.95%, and the maximum luminance of 5.06 × 104 cd/m2, 1.21 × 105 cd/m2, and 2.96 × 103 cd/m2, have been achieved for red, green, and blue QLEDs, respectively. To the best of our knowledge, the red device’s EQE is one of the highest among all inverted red QLEDs. In addition, the extrapolated lifetime of the red QLEDs sets a new record by reaching 8253 h at an initial brightness of 100 cd/m2.