Characterization of polycrystalline electrodeposited CdSe photoelectrodes using photoluminescence spectroscopy

Abstract

We have utilized both photoluminescence (PL) and Raman spectroscopy to nondestructively study the surface of polycrystalline electrodeposited CdSe photoelectrodes as a function of surface preparation and aging procedures. The excitation energy dependence of the PL efficiency at 77 K, which depends on surface band bending, is consistent with increased concentration of shallow levels in electrodeposited CdSe compared with single crystal material. No PL was observed for unannealed CdSe films; for annealed, unaged films the spectra at 77 K were qualitatively similar to those of single crystals in that spectral features could be identified with the A exciton at 1.815 eV and with a donor-acceptor-pair band at 1.70 eV exhibiting phonon replicas. The PL and Raman spectra of light-aged electrodes exhibit features which we identify with the formation of a surface layer of CdS and the presence of mixed compounds CdSxSe1−x, which are formed by chemical exchange with the polysulfide electrolyte during light-induced aging. The PL spectra at 4.2 K for the unaged and dark-aged electrodes exhibit sharp lines in the vicinity of 1.81 eV which we identify as due to bound-exciton recombination, but which differ in energy from those exhibited by the light-aged film.

Photoluminescence of CdSe nanowires grown with and without metal catalyst

“…An unambiguous match between emission peaks (or bands) measured by different groups is difficult, and a full understanding of the origin of each band is still missing. The position and width of several PL features can change for different temperature [53,55], stress [53] or sample contamination [58,61]. Table 1 summarizes the main PL features for bulk CdSe, as reported in Refs.…”

“…Before considering PL from CdSe NWs, it is important to analyze the PL features in bulk and thin film CdSe [9,[53][54][55][56][57][58][59][60]. An unambiguous match between emission peaks (or bands) measured by different groups is difficult, and a full understanding of the origin of each band is still missing.…”

Photoluminescence of high optical quality CdSe thin films deposited by close-spaced vacuum sublimation

“…The presence of these lines is characteristic of the bound-tobound transitions with the participation of donor-acceptors pairs (DAPs) [4,6,20]. In this case the energy of the emitted light, which is associated with the zero-phonon I DAP1 -line, is given by the following equation [21,22]:…”

“…It should be noted that for optoelectronic applications it is very important to have a transparent substrate to the intrinsic (excitonic) light emitted by the active area of thin films. It was found that CdSe films deposited on silicon [4], titanium [5,6] and GaAs [7] substrates manifest intrinsic luminescence, whereas the films deposited on quartz or glass substrates do not show this luminescence [8]. Therefore, it is very important to obtain CdSe films of high optical quality by their deposition on the quartz or glass substrates which are transparent for CdSe intrinsic emission.…”

Study of the correlation between structural and photoluminescence properties of CdSe thin films deposited by close-spaced vacuum sublimation

“…For optoelectronic applications it is also very important to use cheap substrates. Earlier it was found, that CdSe films deposited on silicon [15], titanium [19,20] and GaAs [21] substrates present intrinsic luminescence, whereas the films deposited on quartz substrates do not show this luminescence [22]. Therefore, it is very important to obtain the CdSe films of high optical quality by their deposition on cheap substrates, such as quartz or glass.…”