Vapor-deposited cerium-based halide-organic composites for flexible white electroluminescence

Abstract

White light-emitting diodes (WLEDs) with a single emissive material hold great promise for next-generation lighting, display, and flexible optoelectronic applications. However, it remains difficult to achieve broadband white electroluminescence and efficient carrier utilization within a single emissive material. Here, we report vapor-deposited cerium-based halide-organic composites prepared by multi-source thermal co-evaporation for warm-white electroluminescence. The resulting films exhibit dual-band emission, with a blue band centered at 405 nm and a yellow band centered at 560 nm. Spectroscopic analysis suggests that the blue emission arises from the combined contributions of the Cs₃CeI₆ component and 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) fluorescence, whereas the yellow emission is associated with Ce³⁺-centered 5d–4f emission under a modified local environment induced by interfacial interaction with CBP. Based on these films, warm-WLEDs were fabricated using Cs₃CeI₆@CBP as the emissive layer. The optimized device shows Commission Internationale de l’Eclairage coordinates of (0.38, 0.39), a peak external quantum efficiency of 2.1%, a maximum luminance of 2,678 cd/m², and stable electroluminescence spectra over a broad operating-voltage range. Furthermore, proof-of-concept flexible devices fabricated on polyethylene naphthalate substrates retain stable emission under bending conditions, highlighting the potential of these co-evaporated composite films for flexible light-emitting applications. This work establishes a facile and viable strategy to construct cerium-based halide–organic composite films via thermal co-evaporation for efficient warm-white electroluminescence and flexible light-emitting devices.

Keywords

Rare-earth electroluminescence / white light-emitting diodes / flexible display

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