Mechanoluminescence Color Conversion by Spontaneous Fluorescent-Dye-Diffusion in Elastomeric Zinc Sulfide Composite

Color conversion, long-wavelength light emission by absorbing short-wavelength light, is an attractive approach for developing a broad-color expression technology and is widely used in solid-state lighting, dye-lasers, and colorful displays. Up to now, many papers have been published reporting various mechanoluminescent materials emitting color of ultraviolet, blue, green, orange, and red. However, the strategies of previous reports have focused on color-tuning of mechanoluminescent material itself through newly developing inorganic mechanoluminescent compounds. Here, a new strategy for the color manipulation of mechanoluminescence (ML) is introduced by physically combining fluorescent dyes with existing mechanoluminescent materials. An elastomeric zinc sulfide (ZnS) composite is prepared in a polydimethylsiloxane framework with spontaneously diffused 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), and red luminescence by complete color conversion via DCJTB is demonstrated, which fully absorbed green ML from ZnS. Based on this approach, color-tuning of ML from red to green is successfully achieved and color expression range is expanded by employing electroluminescence (EL). Various-color-emitting EL/ML electromechanical display is demonstrated using color discrepancy between DCJTB employed EL and ML. As the implementation is fairly straightforward, it is believed that present color conversion is a viable and common method to manipulate broader color expression for future ML applications.