Enhanced brightness of methylammonium lead tribromide perovskite microcrystal-based green light-emitting diodes by adding hydrophilic polyvinylpyrrolidone with oleic acid-modified ZnO quantum dot electron transporting layer

In designing highly efficient perovskite light-emitting diodes (PeLEDs), the most significant process is to deposit perovskite film without pinholes and vacancies because discontinuous film results in high leakage current. To fabricate a continuous methylammonium lead tribromide (MAPbBr₃) film, a hydrophilic polymer, polyvinylpyrrolidone (PVP), was added to the MAPbBr₃ precursor solution. Due to the increased wettability of the precursor solution, a full surface coverage of MAPbBr₃-PVP composite film without pinholes was produced. Moreover, zinc oxide (ZnO) quantum dot (QD) was synthesized by hydrothermal process in order to use as an electron transporting layer (ETL), and surface modification of QD was performed by oleic acid (OA) molecules in order to increase spatial distribution in the anti-solvent of perovskite. It was found that, due to the reduced agglomeration of QDs during a spin-coating process, a smooth and highly transparent OA-modified ZnO (OA-ZnO) QD layer was obtained. Thus, the PeLED prepared by using MAPbBr₃-PVP composite film and OA-ZnO QD layer exhibited an excellent device performance of a maximum luminance of 11095.1 cd m⁻² at 6 V and a maximum current efficiency of 6.79 cd A⁻¹ at 4 V. Therefore, it is believed that adding PVP to perovskite materials and using OA-ZnO QD layer as an ETL are effective way to develop perovskite-based high performance LEDs.