Enhancement of Photochromism and Electrochromism in MoO₃/Au and MoO₃/Pt Thin Films

Abstract

Freshly vacuum-evaporated, neat amorphous MoO3 thin films exhibit only UV photochromism. Visible-light photochromism is induced in these films when they are cathodically polarized for a short duration in a nonaqueous electrolyte. The efficiencies of the UV and visible-light photochromism of the MoO3 thin films increase at least 2-fold when they are coated with a thin layer (∼20-nm thickness) of Au or Pt. The enhancement in photochromism is attributed to the presence of a large Schottky barrier at the metal−semiconductor interface, which facilitates electron capture by Au or Pt. The electron capture by the metal produces a longer electron−hole separation lifetime, thereby enhancing the photochromic process. For the electrochromic process, the coloring and bleaching current densities for the MoO3/Au thin-film electrode are about 1.5 and 2.0 times larger than the respective current densities for the MoO3 thin-film electrode. The enhancement in electrochromism is ascribed to the electrocatalytic effect of the gold overlayer. The benefits of surface modifications are (1) inhibition of electron−hole recombination, which enhances photochromism, (2) enhancement of electrochromism, and (3) inhibition of corrosion reaction of surface MoO3.

Flexible electrochromic windows: a comparison using liquid and solid electrolytes

“…In a recent paper 3 we used a dianionic dye to enhance the optical contrast of polypyrrole. Not only the use of dyes 4 , but other aspects are important: sol-gel deposition film methods 5 , temperature of deposition 6 , counterion color influence 7 , oxygen flow during sputtered films 8 , coating the electrochrome with thin gold or platinum layer 9 , etc.…”

Synthesis of photochromic nanoparticles and determination of the mechanism of photochromism

“…[1][2][3][4][5][6][7] Hence, they are expected to be used in sensors and fast optical shutters. In order to construct flexible electronic structures, organic modifiers [8][9][10][11][12][13][14] or lanthanides, [15][16][17][18][19][20][21][22][23][24][25] which have a high principal quantum number, have been employed as photochromic resources until now. Recently, some electrochromic oxide semiconductors have been reported.…”

“…Recently, some electrochromic oxide semiconductors have been reported. [21][22][23][24][25][26][27][28][29][30][31] In these materials, the color change occurs when photons excite electrons into the conduction bands or trap levels, and these electron transitions induce color change. Therefore, some researchers speculated that these electrochromic materials could be used in energy-storable solar cells.…”

Chemically Grown MoO3 Nanorods for Antibacterial Activity Study

“…The tunnel structure facilitates electron-hole pair separation under irradiation and enhances the photochromic performance. As a result of this, MoO 3 have potential applications in the field of photocatalysis [13], electrochromism [14,15], lithium ion batteries [16,17], light emitting diodes etc. [18].…”