Probing Charge Carrier Density in a Layer of Photodoped ZnO Nanoparticles by Spectroscopic Ellipsometry

Abstract

Changes in the optical constants of a layer of ZnO nanoparticles (5 nm diameter) induced by UV illumination in O 2 -free atmosphere are determined by using spectroscopic ellipsometry. The onset of optical absorption of ZnO shifts to higher photon energy after illumination. This is interpreted in terms of a Moss-Burstein shift. From the magnitude of the shift, the charge carrier density in the conduction band after UV illumination was determined to be 2 × 10 19 cm -3 , about one carrier per particle. Kelvin probe measurements give a lower limit for the density of 10 18 cm -3 . The free carrier density after illumination is high enough to explain the formation of quasi-ohmic contacts between ZnO and the polymeric p-type conductor poly(3,4-ethylenedioxythiophene) (PEDOT).

Quasi Two-Dimensional Dye-Sensitized In2O3 Phototransistors for Ultrahigh Responsivity and Photosensitivity Photodetector Applications

“…51 In the proposed process, surface bound oxygen molecules act as electron traps which tend to deplete the semiconductor of mobile electrons. Introduction of holes, most likely via photogeneration due to interband absorption [injection of holes directly to the valence band (VB) of In2O3 (-7.85 eV) 35 from the Al S-D electrodes is highly unlikely due to the large potential barrier], results in desorption of oxygen and to an increase in the electron concentration within the channel.…”

Recent Progress on Solution-Processed CdTe Nanocrystals Solar Cells

“…ZnO film was then deposited onto the CdTe NCs film by solution processing. Ultraviolet irradiation of ZnO films was carried out for the desorption of surface-bound oxygen or carbon dioxide which, in turn, created highly-doped n-type ZnO [37,38]. They finally obtained a champion device with a PCE of 6.9% and up to 90% internal quantum efficiency.…”

“…From the capacitance-voltage (C-V) curves, they concluded that the CdTe/ZnO system operated not like a p-n junction, but more like an i-n junction due to full depletion of the CdTe layer ( Figure 5). carbon dioxide which, in turn, created highly-doped n-type ZnO [37,38]. They finally obtained a champion device with a PCE of 6.9% and up to 90% internal quantum efficiency.…”

“…They obtained a certified PCE of 8.54% with In-doped ZnO thin film. It was found that In-doped ZnO devices had better device performance than those of ZnO NC devices due to the high mobility of In-doped ZnO, carbon dioxide which, in turn, created highly-doped n-type ZnO [37,38]. They finally obtained a champion device with a PCE of 6.9% and up to 90% internal quantum efficiency.…”

Reversible post-breakdown conduction in aluminum oxide-polymer capacitors

“…We note that for ZnO-polymer diode structures, reduction of electrical resistance due to formation of an electrical bilayer at the oxide/polymer interface could be demonstrated. 20 Decay of the conduction induced by DB can be interpreted as recombination in the bilayer across the interface (Fig. 4(c)).…”