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Abstract: A method to prepare wide-band reflection cholesteric liquid crystals (CLCs) films by thermally induced diffusion of dye was proposed. Due to the greatly enhanced UV intensity gradient formed by thermal diffusion of dye, the pitch gradient was formed and fixed after the process of photoinduced polymerization and diffusion of CLC monomers. Using this method, the prepared CLCs film can reflect circularly polarized light over a broad wavelength range of 750–2400nm. The pitch gradient of the CLC film was observed by scanning electron microscopy (SEM). In addition, the influence of dye concentration, thermal diffusion time and thermal diffusion temperature on the consequent pitch gradient was systemically studied. [Copyright &y& Elsevier]