Novel cyan emissive organic–inorganic copper halides: Phase transition, flexible large-area composite film, and multifunctional luminescent applications

Abstract

Organic-inorganic copper halides (OICHs) are attractive due to their outstanding photophysical properties, low toxicity and high abundance. However, the absence of the high-energy emissive OICHs significantly hinders the full-spectrum white light emitting diode (WLED) for high-quality applications and the preparation of large-area films still faces challenges. Herein, we have synthesized a novel cyan emissive (C₁₉H₁₈P)₂CuI₃ by lowering the inorganic anion skeletons dimension in yellow emissive (C₁₉H₁₈P)₂Cu₄I₆, and proposed an UV curing technology to fabricate large-area composite films (10*10 cm²), which is one of the largest reported films based on OICHs. The structure and luminescent properties of (C₁₉H₁₈P)₂CuI₃ could transform into that of (C₁₉H₁₈P)₂Cu₄I₆ under methanol treatment. Notably, the PLQYs of (C₁₉H₁₈P)₂CuI₃ based cyan and (C₁₉H₁₈P)₂Cu₄I₆ based yellow composite films are 78.2% and 96.1%, respectively. Moreover, the cyan and yellow composite films exhibit desirable endurance to air, whose PLQYs could remain 94.12% and 96.26% of its initial value stored in air for 45 days. Remote WLED with high luminous efficiency of 74.44 lm W⁻¹ and powders based cyan-gap free WLED have been fabricated. Additionally, the (C₁₉H₁₈P)₂CuI₃ and (C₁₉H₁₈P)₂Cu₄I₆ based compounds are used as luminescent pastes for encryption applications, and the two composite films are also used for X-ray detection and imaging.