2, Nanjing Tech University, Nanjing, Jiansu, China
Organic-inorganic hybrid perovskites have received great attention due to their high photoluminescence quantum efficiencies, good charge mobilities, high color purity and tunable bandgap. The external quantum efficiency (EQE) of near-infrared (NIR) perovskite light-emitting diodes (PeLEDs) have reached 11.7%.1 However, in conventional PeLEDs, the light extraction efficiency is only ~20% due to the high refractive index of perovskites, resulting in majority of the light generated in the device is confined in the active layers and indium tin oxide layer. Here, we demonstrate a solution-processed microstructure in PeLEDs by adding additive to the perovskite precursor. The microstructure can significantly increase the light out-coupling efficiency by self-assembling low-index grid in the perovskite layer, resulting in a record EQE of NIR PeLEDs. Moreover, the PeLEDs based on this structure also have good stability, with a device lifetime (time to half of the initial brightness) of about 20 hours under a current density of 100 mA cm-2. The results demonstrate that the self-assembled microstructure in perovskites provide promise for further development in solution-processed, high performance LEDs.
 Wang, N. et al. Perovskite light-emitting didoes based on solution-processed self-organized multiple quantum wells. Nat. Photonics 10, 699-704(2016).