Self-Assembled Monolayers Facilitate Simultaneous Enhancements of External Quantum Efficiencies and Circularly Polarized Luminescence Dissymmetry Factors for Chiral Perovskite Red Spin-Light Emitting Diodes.

Abstract

Stemming from the chirality-induced spin-orbit coupling (CISOC), the transfer of spin angular momenta to angular momenta of light can be realized by chiral hybrid perovskites (CHPs) for developing novel spin-light emitting diodes (spin-LEDs). The primary challenge lies in simultaneous enhancements for the electronic charge associated external quantum efficiencies (EQEs) and spin-dependent dissymmetry factor of circularly polarized electroluminescence (g_EL), which severely limits the high-performance spin-LEDs' development. Herein, a self-assembled monolayer (SAM) that acts as an interfacial layer between a nickel oxide (NiO_x) transport layer and a chiral perovskite emissive film has been adopted for red spin-LED fabrications. An optimal EQE of 8.3% and g_EL of 16.3% have been successfully achieved for the red circularly polarized electroluminescence (CPEL) at 725 nm. From the spin-optoelectronic consideration, the well-balanced EQE and g_EL. These are attributed to remarkable fluorescence recombination lifetime improvements, ion migration suppressions, and trap density reductions. Notably, a two times greater spin lifetime (≈27.6 ps) has been obtained by comparing with a control sample (≈12.1 ps). Improved chiral-induced spin-orbit coupling (CISOC) strengths further elevate spin-selective capacities, which consequently promote polarized spin current generation. This study unlocks the challenge and opens a new avenue for constructing high-performance spin-LEDs using the SAM nanotechnology.