Complementary roles of benzylpiperazine and iodine 'vapor' in the strong enhancement of orange photoluminescence from CuI(111) thin film
Abbreviated Journal Title
J. Phys.-Condes. Matter
nanostructures; photoluminescence; defect states; cuprous iodide; CuI; AUGMENTED-WAVE METHOD; STATE SOLAR-CELLS; COPPER IODIDE; HEAVY-HOLE; CUI; GROWTH; LAYER; CONDUCTIVITY; LUMINESCENCE; DEPOSITION; Physics, Condensed Matter
We have employed density functional theory, corrected by the on-site electron-electron repulsion energy U, to clarify the mechanism behind the enhanced orange photoluminescence (PL) of a CuI(1 1 1) thin film conjugated with a benzylpiperazine (BZP) molecule in the presence of an iodine 'vapor' atom. Our results demonstrated that the adsorbed molecule and the 'vapor' atom play complementary roles in producing the PL. The latter, in attaching to the film surface, creates a hole-trapping surface state located similar to 0.25 eV above the valence band-edge of the film, in good agreement with similar to 0.2 eV reported in experiments. Upon photo-excitation of the BZP/CuI(1 1 1) system in the presence of surface iodine 'vapor' atoms, excited electrons are transferred into the conduction band of CuI, and holes are trapped by the 'vapor' atoms. These holes, in turn, quickly relax into the HOMO state of the BZP molecule, owing to the fact that the molecule adsorbs on the film surface in the immediate vicinity of a 'vapor' atom. Relaxed holes subsequently recombine with excited electrons in the conduction band of the CuI film, thereby producing a luminescence peak at similar to 2.1 eV, in qualitative agreement with experimental findings.
Journal of Physics-Condensed Matter
"Complementary roles of benzylpiperazine and iodine 'vapor' in the strong enhancement of orange photoluminescence from CuI(111) thin film" (2014). Faculty Bibliography 2010s. 5980.