High-Performance Blue Perovskite Films and Micro-Arrays for Light-Emitting Diodes with Ionic Liquid Interlayer

Metal halide perovskites have attracted considerable attention for light-emitting diode (LED) applications due to their desirable optoelectronic properties including high brightness and color purity. However, the performance of blue perovskite LEDs (PeLEDs) remains inferior to their red and green counterparts. Herein, an ionic liquid (IL), specifically 1-butyl-3-methylimidazolium tetrafluoroborate is introduced as the interlayer on the hole transport layer (HTL). This IL demonstrates a strong interaction with the perovskite emissive layer, resulting in effective defect passivation and a shallower valence band maximum. Consequently, nonradiative recombination is reduced, and hole injection is enhanced. Additionally, a soft lithography method employing a transfer process is successfully developed that enables precise micropatterning of the perovskite light-emitting layer. Through these advancements, the IL-modified PeLED exhibits pure blue emission at 470 nm with a maximum luminance of 891 cd m-2 and an impressive maximum EQE of 8.3%. Furthermore, the micro PeLED with an IL interlayer achieves a maximum luminance of 400 cd m-2 and a maximum EQE of 3.9%. The introduction of an ionic liquid interfacial modification layer effectively passivates defects and improves the exciton energy transfer by regulating the crystallization growth kinetics of perovskite. This significantly improves the performance and spectral stability of the blue perovskite light-emitting diodes. Additionally, this strategy is also effective for micro perovskite light-emitting diodes fabricated through the transfer of the micro-patterned blocking layer.image