Surface Ligand Engineering toward Brightly Luminescent and Stable Cesium Lead Halide Perovskite Nanoplatelets for Efficient Blue-Light-Emitting Diodes

Abstract

Recently, two-dimensional colloidal perovskite nanoplatelets (NPLs) have attracted great attention as one of the most promising candidate blue emitters due to their large exciton binding energy and precisely tunable thickness. However, the lack of techniques to simultaneously obtain highly emissive and stable perovskite NPLs has limited the successful exploitation of highly efficient perovskite NPL-based optoelectronic devices. Herein, we report the surface ligand-engineering strategy to enhance the photoluminescence quantum yields and stability of perovskite NPLs using a short-chain halide ion-pair ligand. Benefits from the shorter-chain ligand treatment, the electronic conductivity, and carrier injection of perovskite NPL films have also been improved significantly, enabling us to realize highly efficient blue (469 nm) electroluminescence devices with a peak external quantum efficiency of 1.42%, which is among the highest efficiencies of colloidal pure-bromide perovskite NPL-based light-emitting diodes.

The Past, Present, and Future of Metal Halide Perovskite Light‐Emitting Diodes

“…Blue PeLEDs based on CsPbBr 3 nanoplatelets with thickness of less than 4 nm have been demonstrated by several groups, although the device performance is relatively low. [ 29,30 ] Similarly, small‐sized CsPbBr 3 QDs with strong quantum confinement can also exhibit blue emissions and have been used in blue PeLEDs with record EQEs. [ 18 ]…”

Review of blue perovskite light emitting diodes with optimization strategies for perovskite film and device structure

“…5(a)). However, the maximum luminance and EQE degraded as the layers of PNLs decreased, which originated from the severe loss of ligands during the film formation process 74 . Todorovic et al doped Rb + into the precursor solution and synthesized Rb-based colloidal PNLs for the first time by increasing the ratio of OA:OAm from 1:1 to 2:1.…”

“…Donor materials like 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) were inserted on top of the PVK layer, and the excitons could transfer and recombine efficiently in the perovskite film through the Förster resonance energy transfer process (FRET). They believed that a large spectral overlap between the absorption spectra of the acceptor materials (perovskites) and the donor emission spectra is a prerequisite for the FRET process, which gives guidance for selecting suitable HTL materials 74 . Gangishetty et al substituted NiO x with PEDOT:PSS/ TFB/PFI tri-layer HTMs, which not only enhanced the hole transport rate but also prevented nonradiative recombination at the interface due to wide existence of defect sites at the surface of NiO x .…”

Advances in Perovskite Light-Emitting Diodes Possessing Improved Lifetime

“…For example, the EQE of the OA/OLA-based LED decreased to ~20% of its original value, whereas the EQE of the OPA-based one remained >50% after 30 min (Figure 3b). Li et al also adopted the surface ligand engineering strategy to enhance the PLQY and stability of blue perovskite nanoplatelet (NPL) by utilizing a short-chain halide ion-pair ligand DDAB [138]. The shorter-chain ligand treatment improved the electronic conductivity and charge injection of perovskite films, leading to PeLEDs with a peak EQE of 1.42% and enhanced device stability.…”