“…The typical QLED structure is indium tin oxide (ITO)/poly- (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: PSS)/hole transport layer (HTL)/QD/electron transport layer (ETL)/cathode, 16 where polymers 17,18 and metal oxides 6,7,[19][20][21] have been utilized as HTLs and ETLs by spin-coating, respectively. Among them, poly(N-vinylcarbazole) (PVK), widely used as a HTL of QLEDs due to its deep highest occupied molecular orbit (HOMO) energy level, has a low hole mobility of 2.5 Â 10 À6 cm 2 V À1 s À1 , which is much lower than the electron mobility of metal oxides, such as ZnO (B10 À3 cm 2 V À1 S À1 ).…”