Plasmon generation in sputtered Ga-doped MgZnO thin films for solar cell applications

Abstract

The crystalline, electrical, morphological, optical properties and plasmonic behaviour of Ga doped MgZnO (GMZO) thin films grown at different substrate temperatures (200–600 °C) by a dual ion beam sputtering (DIBS) system are investigated. Transmittance value of more than ∼94% in 400–1000 nm region is observed for all GMZO films. The particle plasmon features can be detected in the absorption coefficient spectra of GMZO grown at 500 and 600 °C in the form of a peak at ∼4.37 eV, which corresponds to a plasmon resonance peak of nanoclusters formed in GMZO. The presence of such plasmonic features is confirmed by ultraviolet photoelectron spectroscopy measurements. The values of particle plasmon resonance energy of various nanoclusters are in the range of solar spectrum, and these can easily be tuned and excited at the desirable wavelengths while optimizing the efficiency of solar cells (SCs) by simple alteration of DIBS growth temperature. These nanoclusters are extremely promising to enhance the optical scattering and trapping of the incident light, which increases the optical path length in the absorber layer of cost-effective SCs and eventually increases its efficiency.

Investigation of Dual-Ion Beam Sputter-Instigated Plasmon Generation in TCOs: A Case Study of GZO

“…The plasmonic features are clearly observed in the extinction coefficient spectra of both GZO 200 and GZO 300 thin films in the form of the peak at 4.08 and 3.72 eV, respectively, which might correspond to the plasmon resonance peak of the nanoclusters formed in the corresponding thin film. 24 Further, the insets in Figure 3a,b are the corresponding Tauc's plots, which confirm the E g of 3.54 and 3.32 eV for GZO 200 and GZO 300 , respectively. The observed decrement in the value of E g for GZO 300 sample when compared to that of GZO 200 may be due to the metallic clusters formation at the thin film surface.…”

“…These peaks appear due to the additional absorption in the films, which might have been caused by particle plasmons produced by metal or metal oxide nanoclusters in the GZO 200 and GZO 300 thin films. 24,28,56 The spectral variations in the refractive index (n) and the extinction coefficient (k) of the GZO 200 and GZO 300 films are plotted in Figure 2c,d, acquired from data conversion using the dielectric functions as depicted in Figure 2a,b. The maximum value of n is 2.2 and 3.37 for GZO 200 and GZO 300 , respectively.…”

“…Theoretically, the VBP energy, ℏω b , of the particle material in the free electron approximation is evaluated by eq 3. 24,36,37,68…”

“…Here, we report a novel process of plasmon generation in TCOs over a wide spectral range of 1.87–10.48 eV, deploying dual-ion beam sputtering (DIBS) system. By exploiting the DIBS system, the formation of the plasmonic nanoclusters has been elucidated in our earlier publications. − In continuation to our earlier studies on sputter-instigated plasmon generations, further extending our work on metal and metal oxide cluster formations and their effects on plasmon generations, additional studies are performed as follows: (1) effect of growth temperature on the electrical and structural properties of the TCO thin films grown by utilizing a secondary source; (2) influence of material properties on metal and metal oxide nanoclusters formation; (3) impact of physical parameters, i.e., size, surface coverage, interparticle distance, etc., of nanoclusters on the tuning of plasmonic properties; (4) quantification of the plasmon energies within broad plasmonic peaks; (5) finding the possibility of a particular type of plasmon, i.e., particle plasmon (in the air, or within material), surface plasmon, and bulk plasmon generation at air/thin film interface, and within a thin film.…”

Thermal stability of ultra-wide-bandgap MgZnO alloys with wurtzite structure

“…Advances in the material issues of Mg x Zn 1−x O thin films may lead to applications including MgZnO p-n heterostructure light-emitting devices that operate at 355 nm [14], plasmonic generation in Ga-doped MgZnO for solar cell technologies [15], and solar-blind UV detectors with a cutoff at 270 nm [16]. Additionally, it has been found that the MgZnO thin film transistors at the small Mg composition range Mg 0.06 Zn 0.94 O have better device performance than pure ZnO channel devices [17].…”