Optimization of Low‐Dimensional Components of Quasi‐2D Perovskite Films for Deep‐Blue Light‐Emitting Diodes

Abstract

Compared to efficient green and near‐infrared light‐emitting diodes (LEDs), less progress has been made on deep‐blue perovskite LEDs. They suffer from inefficient domain [various number of PbX6− layers (n)] control, resulting in a series of unfavorable issues such as unstable color, multipeak profile, and poor fluorescence yield. Here, a strategy involving a delicate spacer modulation for quasi‐2D perovskite films via an introduction of aromatic polyamine molecules into the perovskite precursor is reported. With low‐dimensional component engineering, the n1 domain, which shows nonradiative recombination and retarded exciton transfer, is significantly suppressed. Also, the n3 domain, which represents the population of emission species, is remarkably increased. The optimized quasi‐2D perovskite film presents blue emission from the n3 domain (peak at 465 nm) with a photoluminescence quantum yield (PLQY) as high as 77%. It enables the corresponding perovskite LEDs to deliver stable deep‐blue emission (CIE (0.145, 0.05)) with an external quantum efficiency (EQE) of 2.6%. The findings in this work provide further understanding on the structural and emission properties of quasi‐2D perovskites, which pave a new route to design deep‐blue‐emissive perovskite materials.

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

“…We also examine the spectral stability of our devices at a constant current density of 5 mA cm −2 (with initial luminance ranging from ~200 to ~600 cd m −2 for different devices). Although the operational lifetime is no better than those in previously reported blue PeLEDs (with T 50 around 1–2 min) 8 , 11 , 12 , 20 , we observe no spectral shift even after 10 min of operation (Supplementary Fig. 15 ).…”

“…Current efforts in blue PeLEDs largely take advantage of quantum confinement effects for bandgap engineering, i.e. using mixed dimensional perovskites or colloidal perovskite nanocrystals 8 – 10 . Although impressive progress has been achieved in developing sky-blue PeLEDs (with CIEy > 0.15) (Supplementary Table 1 ) 11 , there are increasing difficulties to realize blue emission using these strategies.…”

Mixed Halide Perovskites for High-Efficiency and Spectrally Stable Blue Light-Emitting Diodes

“…We also examine the spectral stability of our devices at a constant current density of 5 mA cm -2 (with initial luminance ranging from ~200 to ~600 cd m -2 for different devices). Although the operational lifetime is no better than those in previously reported blue PeLEDs (with T50 around 1~2 min) 8,11,12,20 , we observe no spectral shift even after 10 minutes of operation ( Supplementary Fig. 15).…”

Dimension control of in situ fabricated CsPbClBr2 nanocrystal films toward efficient blue light-emitting diodes

“…4d . A higher proportion of small- n ( n = 1, 2) domains is obtained in PEABr-only films, which may lead to the non-radiative recombination and inefficient energy transfer and therefore result in a low-efficiency emission 58 . The formation of such small- n domains is inhibited in DPPABr-only films.…”