CdO as the Archetypical Transparent Conducting Oxide. Systematics of Dopant Ionic Radius and Electronic Structure Effects on Charge Transport and Band Structure

Mendelsberg

Applied Surface Science

et al. 2013

Title AbstractIndium doped cadmium oxide (CdO:In) films with different In concentrations were prepared on low-cost glass substrates by pulsed filtered cathodic arc deposition (PFCAD). It is shown that polycrystalline CdO:In films with smooth surface and dense structure are obtained. In-doping introduces extra electrons leading to remarkable improvements of electron mobility and conductivity, as well as improvement in the optical transmittance due to the Burstein-Moss effect. CdO:In films on glass substrates with thickness near 230 nm show low resistivity of 7.23×10 -5 Ωcm, high electron mobility of 142 cm 2 /Vs, and mean transmittance over 80% from 500-1250 nm (including the glass substrate). These high quality pulsed arc-grown CdO:In films are potentially suitable for high efficiency multi-junction solar cells that harvest a broad range of the solar spectrum. Keywords:In doped cadmium oxide; pulsed filtered cathodic arc deposition; transparent conductors IntroductionTransparent conducting oxides (TCOs) have attracted much attention due to their tremendous importance in optical and electrical applications such as displays, touch-screens, thin film solar cell technology and for transparent conducting electrodes in general [1,2]. For solar cell applications, high mobility TCO contacts with a sheet resistance of <10 Ω/□ and an optical transmission >80% over the visible to near infrared wavelengths (bandgap >3 eV) can enhance the efficiency [3]. This is particularly effective for multi-junction solar cells which consist of different semiconductor stacks with appropriately matched bandgaps that are tuned to increase the spectral response over the entire solar spectrum [4]. Therefore, in addition to maintaining high conductivity, improving the visible to near infrared transparency of TCO films is of great importance for applications in high performance multi-junction solar cells.

Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 84%

Transparent and conductive indium doped cadmium oxide thin films prepared by pulsed filtered cathodic arc deposition

Mendelsberg

Applied Surface Science

et al. 2013

Adv. in Nat. Appl. Sci.

“…α(hv)=B〖(hv-E_g)〗^r (5) Where (B) is constant involving the properties of the bands,(υ) frequency of incident photon ,(r) is a constant depending on the nature of transition. From figure (7) It can be observed that the energy gap increased with increasing of Cu constrationfrom(2-3)eV.…”

Section: 3optical Propertiesmentioning

confidence: 99%

“…[5][6] Cadmium oxide has a high conductivity resulting from the presence of cadmium atoms in interstitial sites or due to oxygen vacuums [3]. Cadmium oxide has a high absorption factor that can be used in solar systems to increase its efficiency in photovoltaic cells and is used as window layers in Hetrojunction Solar Cells and transparent electrodes in solar cell technology.…”

Section: Introductionmentioning

confidence: 99%

Studying Structural, Morphological And Optical Properties of Cadmium Oxide

2018

CdO is an n-type semiconductor with a rock-salt crystal structure (fcc) and possesses a direct band gap of 2.2 eV . Its high electrical conductivity and high optical transmittance in the visible region of solar spectrum along with a moderate reflective index make it useful for various applications, photodiodes, gas sensors, etc. CdO and CdO:Cuthin films have been prepared on glass substrates at 380C°substrate temperature by the chemical spray pyrolysis(CSP) method using an aqueous solution with varying copper concentrations. The thickness of the films have been measured to be (200±5)nm. The films have been characterized to evaluate the structure ,morphology, transmittance and optical energy band gab. X-ray diffraction(XRD) studies show that the films are polycrystalline with cubic structures. The optical band gab energies and types of optical transition and absorption of the films have been determined from the optical transmittance spectra. The optical absorption studies in the wavelength range 300-900 nm show that band gap energy values of the films increase from (2 to 3)eV as the Cu concentration increases.

“…12 NB semiconductors are colored or black when closed to stoichiometry, which is the case of β-PbO 2 , but may potentially become transparent when donor doped to high carrier concentrations, as it has been found for CdO, 13,14 thanks to the blue-shift of the optical band gap, following the Moss-Burstein effect. 15,16 The shift arises because the Fermi energy lies in the conduction band for heavy n-type doping and, consequently, the filled states block optical excitation.…”

mentioning

confidence: 98%

Conducting Behavior of Crystalline α-PbO2 as Revealed by DFT Calculations

2017

PbO 2 is one material that has recently emerged as potential transparent conducting oxide for applications in the modern opto-electronic industry. In this work the electronic structure of the α-PbO 2 polymorph has been investigated, aiming to contribute to the understanding of its high levels of conductivity. DFT calculations using B3LYP hybrid density functional and considering long range interactions among the atoms have been performed. A direct band gap of 0.90 eV has been found, compatible with high conductivity values. Although the stoichiometric material is somewhat transparent, the band structure indicates that appropriated modifications in the material Fermi level can be performed in order to decrease the absorption of light. Charge distribution plus overlap population analysis show that the material is predominantly ionic. The charge distribution throughout the material is strongly dependent on the crystal direction. Results suggest that α-PbO 2 can be potentially more interesting for opto-electronic purposes than the β polymorph.