Despoina Gkeka1,Murali Gedda1,Mohamad Nugraha1,Jafar Khan1,Emre Yengel1,Iain Hamilton1,Frederic Laquai1,Donal Bradley1,Thomas Anthopoulos1
KAUST1
Despoina Gkeka1,Murali Gedda1,Mohamad Nugraha1,Jafar Khan1,Emre Yengel1,Iain Hamilton1,Frederic Laquai1,Donal Bradley1,Thomas Anthopoulos1
KAUST1
Low-dimensional hybrid perovskites have recently emerged as promising candidates for light-emitting diode (LED) applications due to their outstanding physical characteristics that include high photoluminescence quantum yield (PLQY), color purity, operating stability and processing versatility. Unfortunately, controlling the microstructure of the solid layers during solution deposition remains very challenging. Introducing molecular additives into the perovskite layer during processing has recently emerged as an effective strategy towards improving both the quality of the formed perovskite layer and the overall performance of the ensuing perovskite LEDs (PeLEDs).<br/>Here we report on the development of highly efficient green PeLEDs based on blends of the quasi-two (q2D) dimensional perovskite PEA<sub>2</sub>Cs<sub>4</sub>Pb<sub>5</sub>Br<sub>16 </sub>and a known small molecule (SM) organic semiconductor. The presence of the SM enables the formation of single-crystal-like q2D perovskite domains that are uniform, large in size and highly luminescent. We show that combining the q2D-Perovskite:SM blends with self-assembled monolayers (SAMs) as the hole-injecting layers (HILs), results in green emitting PeLEDs that exhibit greatly enhanced performance over pristine perovskite LEDs including, maximum external quantum efficiency (EQE) of 18.6 %, current efficiency of 46.31 cd/A, maximum brightness of ≈ 45,000 cd m<sup>−2</sup>, and a longer operational lifetime. Using a complementary suite of characterization techniques, we show that the improved performance of the blend PeLEDs to originate from multiple synergistic effects including, the enhanced hole-injection due to SAM HILs and the single crystal-like quality of the perovskite phase. Our work highlights perovskite:organic semiconductor blends as promising strategy towards high performance PeLEDs, while the use of SAM HILs creates new opportunities for simpler and more reliable materials for application in next generation light-emitting diodes.