Vacancy-Ordered Double Perovskite Cs 2 TeI 6 Thin Films for Optoelectronics.

Alternatives to lead- and tin-based perovskites for photovoltaics and optoelectronics are sought that do not suffer from the disadvantages of toxicity and low device efficiency of present-day materials. Here we report a study of the double perovskite Cs ₂ TeI ₆ , which we have synthesized in the thin film form for the first time. Exhaustive trials concluded that spin coating CsI and TeI ₄ using an antisolvent method produced uniform films, confirmed as Cs ₂ TeI ₆ by XRD with Rietveld analysis. They were stable up to 250 °C and had an optical band gap of ∼1.5 eV, absorption coefficients of ∼6 × 10 ⁴ cm ^-1 , carrier lifetimes of ∼2.6 ns (unpassivated 200 nm film), a work function of 4.95 eV, and a p-type surface conductivity. Vibrational modes probed by Raman and FTIR spectroscopy showed resonances qualitatively consistent with DFT Phonopy -calculated spectra, offering another route for phase confirmation. It was concluded that the material is a candidate for further study as a potential optoelectronic or photovoltaic material.
Competing Interests: The authors declare no competing financial interest.
(Copyright © 2020 American Chemical Society.)