Efficient Orange Light-Emitting Diodes from Nontoxic Organic–Inorganic Hybrid Copper Halides Enabled by Nonionic Surfactant Chemisorption

Abstract

Ternary copper halides with an eco-friendly property have emerged as attractive candidates to replace toxic lead-containing perovskites for light-emitting diodes (LEDs), yet achieving long-wavelength electroluminescence remains unexplored. Herein, we report the first realization of orange-emitting LEDs (595 nm) based on nontoxic organic-inorganic PEA₄Cu₄I₄ (PEA = β-phenylethylamine) films enabled by a nonionic surfactant poly(propylene glycol) bis(2-aminopropyl ether) (APPG) chemisorption. Experimental and theoretical analyses rationalize that the APPG additive has strong chemisorption with the Cu-I framework within the grain boundaries of PEA₄Cu₄I₄ films, which not only improves the film's morphology but also passivates the iodine vacancy defects. Moreover, the APPG additive can raise the ionization energy and increase the carrier mobility of PEA₄Cu₄I₄ films, thereby balancing the charge transport. Consequently, we achieve orange LEDs made from APPG-treated PEA₄Cu₄I₄ films, showing an external quantum efficiency of 1.21%, and the operational stability of the treated device is greatly prolonged, resulting from the suppressed iodine ion migration.