High-Performance Vacuum-Deposited Perovskite Light-Emitting Diodes with the Assistance of Small-Molecule Hole-Transport Materials

Metal halide perovskite light-emitting diodes (PeLEDs) rapidly advance in their external quantum efficiency (EQE), highest brightness, and operation lifetime in recent years. However, solution-processed PeLEDs usually encounter uniformity issues of crystal growth, which make them difficult to realize large-area fabrication, despite their outstanding device performance. With the intrinsic advantage of high reproducibility and uniformity in thin-film quality, vacuum-deposited PeLEDs possess a great potential in industrial mass production. Although breakthroughs have been observed in vacuum-deposited PeLEDs recently, the strategy of choosing their hole-transport materials (HTMs) still follows the experience of solution-processed PeLEDs. In this work, we demonstrated a simple approach to significantly improve vacuum-deposited perovskite PeLEDs by inserting a thin vacuum-deposited interfacial organic layer between 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) HTM and perovskite emission layer (EML). With the evidence of X-ray photoelectron spectroscopy (XPS), we showed that the interfacial layer successfully inhibited the formation of metallic Pb⁰ caused by the TAPC/perovskite chemical degradation. The device with the interfacial layer exhibited a luminance of 55968 cd m^-2, a current efficiency of 33.2 cd A^-1, and an EQE of 9.40%, which was a 4-fold enhancement compared to that of the device without the interfacial layer. The results of EQE and brightness are among the highest reported values in vacuum-deposited PeLEDs.