Evidence for photogenerated intermediate hole polarons in ZnO

  • chair:

    Sezen, H. / Shang, H. / Bebensee, F. / Yang, C. / Buchholz, M. / Nefedov, A. / Heissler, S. / Carbogno, C. / Scheffler, M. / Rinke, P. / Wöll, C. (2015) 
  • place:

    Nature Communications, 6, 6901(1-4), doi:10.1038/ncomms7901 
  • Date: April 2015

Abstract

Despite their pronounced importance for oxide-based photochemistry, optoelectronics and photovoltaics, only fairly little is known about the polaron lifetimes and binding energies. Polarons represent a crucial intermediate step populated immediately after dissociation of the excitons formed in the primary photoabsorption process. Here we present a novel approach to studying photoexcited polarons in an important photoactive oxide, ZnO, using infrared (IR) reflection–absorption spectroscopy (IRRAS) with a time resolution of 100 ms.

For well-defined (10-10) oriented ZnO single-crystal substrates, we observe intense IR absorption bands at around 200 meV exhibiting a pronounced temperature dependence. On the basis of first-principles-based electronic structure calculations, we assign these features to hole polarons of intermediate coupling strength. 

 

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