Highly stable and efficient tandem organic light-emitting devices with intermediate connectors using lithium amide as n-type dopant

In this work, we report thermally decomposable lithium amide (LiNH2) feasible to function as an effective n-type dopant for intermediate connectors in tandem organic light-emitting devices (OLEDs). Metallic lithium, which is released from the decomposition process of LiNH2, is proved by X-ray photoelectron spectroscopy and responsible for n-type electrical doping of electron transporting materials. We demonstrate that tandem OLEDs using LiNH2 and Cs2CO3 as n-type dopants, respectively, give a comparable electroluminescence efficiency and, moreover, the device with LiNH2 has far longer operational lifetime. The results therefore highlight the significance of selecting suitable n-type dopant in intermediate connectors to fabricate high-stability tandem OLEDs.