| AVS 62nd International Symposium & Exhibition | |
| Energy Frontiers Focus Topic | Monday Sessions |
| Session EN+AS+EM+NS+SE+SS+TF-MoA |
| Session: | Solar Cells II |
| Presenter: | Mirella Vargas, The University of Texas at El Paso |
| Authors: | M. Vargas, The University of Texas at El Paso N.R. Murphy, Air Force Research Laboratory R.V. Chintalapalle, The University of Texas at El Paso |
| Correspondent: | Click to Email |
Tungsten oxide (WO3) is a well-established n-type semiconductor possessing unique optical and electronic properties. WO3 has become the most interesting inorganic material for electrochromic applications due to the reversible spectral absorption properties associated with WO3. WO3 thin films and nanostructures exhibit an optical band gap that permits efficient use of the solar spectrum including absorption in the blue part of the visible region and the ultraviolet region, as well as a high transmission region that extends from the near-infrared (IR) to the visible spectrum. Coupled with good electronic transport properties, photosensitivity, and chemical integrity, WO3-based materials are attractive for applications related to sustainable energy production including energy efficient windows and architecture, photoelectrochemical (PEC) water-splitting, photocatalysis and solar cells. Anion or cation doping into WO3 has been extensively studied as this offers the opportunity to tailor the transport properties that may influence the efficiency of solar driven devices. Titanium doping into WO3 has proven to enhance the electrochromic response and the cyclic lifetime by a factor of five in PEC devices. In the present case a systematic investigation of progressively increasing the Ti content in the W-Ti target for reactive sputtering has been employed to tune the structure, chemistry, and properties of the films. Tungsten-titanium (W-Ti) mixed oxide thin films were fabricated using reactive sputtering of W-Ti alloy targets with Ti content ranging from 0 to 30 wt.%. X-ray photoelectron spectroscopy confirms the existence of W and Ti in their highest oxidation states of +6 and +4, respectively. Quantification of binding energy shifts for W and Ti core-level transitions confirms the formation of WO3-TiO2 composite oxide films. Optical analyses made from spectrophotometry measurements indicate a decrease in band gap with a discrete amount of Ti incorporation. The band gap decreases with increasing Ti from 3.0 eV to 2.5 eV. Such films are expected to have the possibility for tuning the electrical conductivity while retaining the optical transparency to make them efficient for photoelectrochemical cells and photovoltaics.