High-Efficiency Cu–In–S Quantum-Dot-Light-Emitting Device Exceeding 7%

We report on the unique synthesis of heterostructured core/shell Cu–In–S (CIS)/ZnS quantum dots (QDs) from a shelling perspective and fabrication of high-efficiency QD light-emitting diodes (QLEDs) with a standard device architecture. Onto CIS core QDs ZnS shelling of extraordinarily long duration is attempted along with the multiple injections of shell precursors. Three CIS/ZnS QDs obtained through different shelling periods of time are prepared and then individually employed as an emitting layer (EML) of solution-processed, multilayered QLED comprising a hole transport layer of poly((9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-s-butylphenyl))diphenyl-amine) (TFB) and an electron transport layer of ZnO nanoparticles. We observe a remarkable dependence of device performance on the type of QDs and attribute this presumably to different QD heterostructural details as a function of shelling duration. Our best device integrated with the longest-shelled QDs displays excellent current efficiency of 18.2 cd/A and external quantum efficiency of 7.3%, corresponding to the record-high values among CIS QLEDs reported.