Quasi-two-dimensional perovskite light emitting diodes for bright future

Efficient Red-Emissive Circularly Polarized Electroluminescence Enabled by Quasi-2D Perovskite with Chiral Spacer Cation

Perovskites are promising environmentally sustainable materials for circularly polarized electroluminescence (CPEL). While another chiral nonemissive layer is required for the developed perovskite-based CPEL, we report herein a highly efficient circularly polarized electroluminescence based on a single layer of quasi-2D perovskite with achiral phenethylammonium iodide (PEAI) and chiral S/R-1-(1-naphthyl)ethylammonium iodide (S/R-NEAI) as dual spacer cations. The quasi-2D perovskite was further passivated by carbazole-functionalized phosphonium. The as-fabricated film exhibits not only a circular dichroism (CD) signal but also prominent circularly polarized luminescence (CPL) activity with a maximum photoluminescence dissymmetry factor (g_lum) of ∼2.1 × 10^-3. More importantly, a highly efficient, spin-polarized light-emitting diode (LED) was fabricated based on the in situ passivated quasi-2D perovskite with a peak external quantum efficiency of 3.7% and a maximum electroluminescence dissymmetry factor (g_EL) of ∼4.0 × 10^-3.

High-Quality Patterning of CsPbBr3 Perovskite Films through Lamination-Assisted Femtosecond Laser Ablation toward Light-Emitting Diodes

Metal halide perovskites have exhibited promising potential for practical applications such as image sensors and displays benefiting from their outstanding optoelectronic properties. However, owing to the instability of the perovskite materials, producing patterned perovskite films with adequately high quality and high precision for such practical applications poses a challenge for existing patterning methods. Herein, the lamination-assisted femtosecond laser ablation (LA-FsLA) technique was successfully applied to fabricate patterned CsPbBr₃ films with sufficiently high quality and high precision. A sandwich-laminated structure (glass/CsPbBr₃/glass) was introduced to avoid the impact of debris on the patterned perovskite film. As a result, arbitrarily patterned perovskite films with high quality, submicron precision, and well-defined edges were successfully prepared. Moreover, the light-emitting diodes (LEDs) based on the patterned perovskite films also exhibit good emission characteristics. This work provides a promising strategy for the fabrication of patterned perovskite films with adequately high quality and high precision toward perovskite-based optoelectronic devices.

Plasmonic and Graphene-Functionalized High-Performance Broadband Quasi-Two-Dimensional Perovskite Hybrid Photodetectors

Quasi-two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted extensive attention, owing to their excellent optoelectronic tunability and moisture stability compared with three-dimensional perovskite counterparts and show great potential for application in photodetectors (PDs). However, owing to the unavoidable grain boundary defects of perovskite polycrystalline films, the photocurrent is limited by poor light absorption and charge mobility. Therefore, the preparation of quasi-2D perovskite films with strong light trapping and high charge mobility has been challenging. In this study, novel broadband quasi-2D perovskite (BA)₂(FA)_n-1Pb_nI_3n+1 hybrid-structure PDs with good stability were fabricated by combining both monolayer graphene and Au square nanoarrays. The hybrid system using both graphene and Au square nanoarrays effectively improved the carrier mobility and light absorption and simultaneously maximized light trapping and light-induced carrier extraction, which resulted in PDs with greatly enhanced photocurrent in the visible and near-infrared range. The graphene-Au array-perovskite-based PDs had a low dark current of 10^-10 A, large on/off ratio of 10⁴, high responsivity of 18.71 A W^-1, and detectivity of 2.21 × 10¹³ Jones. The responsivity and detectivity were two orders of magnitude higher than those of PDs based only on perovskites. This work demonstrates a promising and feasible device based on the coupling of a gold array, layered graphene, and quasi-2D perovskites, which shows great potential for the development of high-performance broadband perovskite PDs.