Mahesh Gangishetty1 Shaocong Hou1 Qimin Quan1 Dan Congreve1

1, Rowland Institute at Harvard, Cambridge, Massachusetts, United States

Interest in light emitting diodes utilizing perovskite nanocrystals has exploded in the past several years. Indeed, green and red devices have shown high efficiencies and brightness. Blue devices, however, have lagged significantly behind. In this work, we show that a key reason for the lag is the architecture of the device itself. By monitoring their brightness and lifetime, we demonstrate that the perovskite nanocrystals are significantly impacted by the presence of nickel oxide, a hole transport layer in one of the highest efficiency devices to date. We develop a transport layer structure which maintains robust dot emission, allowing the LEDs to achieve external quantum efficiencies of 0.50% at 469 nm, much higher than previous devices at that wavelength. We demonstrate that these improvements are most robust for blue devices, and the gains reduce as we tune the emission energy back towards the green. The improvements demonstrated open the door towards efficient blue perovskite LEDs.