Quantifying the Performance of P-Type Transparent Conducting Oxides by Experimental Methods

Abstract

Screening for potential new materials with experimental and theoretical methods has led to the discovery of many promising candidate materials for p-type transparent conducting oxides. It is difficult to reliably assess a good p-type transparent conducting oxide (TCO) from limited information available at an early experimental stage. In this paper we discuss the influence of sample thickness on simple transmission measurements and how the sample thickness can skew the commonly used figure of merit of TCOs and their estimated band gap. We discuss this using copper-deficient CuCrO2 as an example, as it was already shown to be a good p-type TCO grown at low temperatures. We outline a modified figure of merit reducing thickness-dependent errors, as well as how modern ab initio screening methods can be used to augment experimental methods to assess new materials for potential applications as p-type TCOs, p-channel transparent thin film transistors, and selective contacts in solar cells.

Band edge evolution of transparent ZnM2IIIO4 ( MIIWahila1, Lebens-Higgins2, Jackson3 et al. 2019Phys. Rev. B16180View full textAdd to dashboardCite

“…Shown in Fig. 2(b), band gaps can be quantitatively determined from absorption spectra using Tauc analysis, where (αhν) 1/r is plotted versus hν using an r value corresponding to the type of optical transition occurring between the band edges [41,42]. After fitting a line to the predominantly linear region of this Tauc plot, the x intercept of said line provides an approximate value for the onset of optical absorption (i.e., the band gap), provided there is negligible background signal at photon energies below the absorption onset.…”

Crystallographic Characterisation of Ultra-Thin, or Amorphous Transparent Conducting Oxides—The Case for Raman Spectroscopy

“…Alternative methods, with larger scattering cross-section and sensitivity to local bond structures, rather than long-range order, are hence sought for. Particularly for recently developed amorphous or non-crystalline p-type TCOs gaining additional information on the local bond structure will be helpful to gain insights on the doping mechanisms [21][22][23][24][25][26][27].…”

“…All values include the substrate. The relatively low transmission is caused by high reflectivity by interference for the specific film thickness [24]. The film thickness was measured by X-ray reflection.…”

Optical Losses of Frontal Layers in Superstrate CdS/CdTe Solar Cells Using OPAL2

“…Basically, we can assume that n = n when only the real part of the refractive index is considered in the transparent region. However, at resonant frequencies along both sides of the transparency sphere, absorption becomes significant, and the imaginary part of the refractive index must be regarded so that n* = n + ik is utilized [47].…”

“…The flux of photons into each device may be controlled by the reflected flux that is emitted and consumed by each interface. Reflectance is given by [47]:…”