Good Charge Balanced Inverted Red InP/ZnSe/ZnS-Quantum Dot Light-Emitting Diode with New High Mobility and Deep HOMO Level Hole Transport Layer

Here, we report efficient and stable indium phosphide (InP) based inverted red quantum dot light-emitting diodes (QLEDs) using a new high mobility and deep HOMO level hole transport layer (HTL) and an optimized sol–gel ZnMgO layer. A new hole transport material, DBTA, containing rigid dibenzothiophene and tertiary amine units has been designed with high hole mobility and a deep HOMO level to inject holes faster into the InP-QDs. Also, to decrease the electron transporting property of the ZnMgO NPs, a sol–gel ZnMgO layer with optimum magnesium content (17%), low-temperature annealing (180 °C), and a self-aging process is used on the transparent electrode. The high mobility DBTA and an optimized sol–gel Zn0.83Mg0.17O layer with the self-aging process are responsible for achieving good charge balance and suppressing nonradiative losses in InP-QLED. The fabricated QLED with DBTA and optimized sol–gel Zn0.83Mg0.17O exhibited an external quantum efficiency of 21.8%, current efficiency of 23.4 cd/A, and operating lifetime (LT50) of 1095 h at 1000 cd/m2.