Investigating multicolour photochromic behaviour of AgCl and AgI thin films loaded with silver nanoparticles

Multicolour photochromic behaviour in light-sensitive Ag-AgCl and Ag-AgI thin films at room temperature was investigated and compared. Although it seemed that the Ag-Ag halide thin films have similar optical properties, their optical responses to a monochromatic laser beam are completely different. It is shown that Ag-AgCl thin film changes its colour under light irradiation to the same colour of the incident light, regardless of the polarization state of the laser beam. In contrast, the Ag-AgI thin film changes to complementary colours of the incident beam. The different optical behaviours of Ag-AgCl and Ag-AgI thin films are due to the different electrical properties of AgCl and AgI thin films. Moreover, the multicolour photochromic behaviour is due to the changes of absorption spectra and surface morphology of silver nanoparticles on silver-haide thin film. These changes are the result of excitation of localized surface plasmon resonance of silver nanoparticles by the laser beam and charge transfer between silver nanoparticles and silver-halide thin films.