Boosting Cu─In─Zn─S‐based Quantum‐Dot Light‐Emitting Diodes Enabled by Engineering Cu─NiO_x/PEDOT:PSS Bilayered Hole‐Injection Layer

Abstract

The imbalance of charge injection is considered to be a major factor that limits the device performance of cadmium‐free quantum‐dot light‐emitting diodes (QLEDs). In this work, high‐performance cadmium‐free Cu─In─Zn─S(CIZS)‐based QLEDs are designed and fabricated through tailoring interfacial energy level alignment and improving the balance of charge injection. This is achieved by introducing a bilayered hole‐injection layer (HIL) of Cu‐doped NiOx (Cu─NiOx)/Poly(3,4‐ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS). High‐quality Cu─NiOx film is prepared through a novel and straightforward sol–gel procedure. Multiple experimental characterizations and theoretical calculations show that the incorporation of Cu2+ ions can regulate the energy level structure of NiOx and enhance the hole mobility. The state‐of‐art CIZS‐based QLEDs with Cu─NiOx/PEDOT:PSS bilayered HIL exhibit the maximum external quantum efficiency of 6.04% and half‐life time of 48 min, which is 1.3 times and four times of the device with only PEDOT:PSS HIL. The work provides a new pathway for developing high‐performance cadmium‐free QLEDs.

High-performance QLED research based on direct photo-crosslinking of PEDOT:PSS

“…For ease of description, PEDOT Al 4083 will be written as 4083 and PEDOT PH1000 will be written as PH1000. 13–18 Commercial 4083 and PH1000 exhibit comparable pH values (approximately 2.0 at 20 °C), but the PEDOT:PSS ratio is different, with 4083 maintaining a ratio of 1 : 6 and PH1000 a ratio of 1 : 2.5. The optical crosslinking of PEDOT:PSS holds profound implications for the fabrication of micro–nano structured optoelectronic devices.…”