Inorganic perovskite light emitting diodes with ZnO as the electron transport layer by direct atomic layer deposition

Inorganic n-type metal oxide materials, i.e., ZnO have been developed and employed as interface layers for energy level matching and electron transport in order to achieve high performance perovskites based optoelectronic devices. In this work, we successfully apply atomic layer deposition (ALD) technique to deposit ZnO directly on top of CsPbBr3 to serve as the electron transport layer. A regular perovskite light emitting diode (PeLED) in a configuration of glass/ITO/PEDOT: PSS/CsPbBr3/ZnO/Ag was fabricated. In the CsPbBr3 emitting layer, polyethyleneimine ethoxylated (PEIE) dissolved in an anti-solvent chlorobenzene (CB) was introduced to assist the nucleation and crystal growth of perovskite films, as well as providing surface reactive sites for ALD deposition of ZnO layer particularly. The ALD deposition temperature on the growth, crystallinity and morphology of ZnO and subsequent device performance was investigated. We obtained PeLEDs of the best performance with the best current and external quantum efficiency (EQE) of 0.49 cd/A and 0.14%, respectively, which is as 14 folds high as an inorganic CsPbBr3 device using F8 as the electron transport layer reported previously.