skip to content

Thunder Bay Regional Health Research InstituteIn partnership with the Thunder Bay Regional Health Sciences Centre

Bringing Discovery to Life

Health Sciences Discovery Fund - Donate Now

Follow us on Twitter Find us on Facebook Check out our YouTube videos

New Publication - August 8, 2014

Comparative Study of the Photodarkening Relaxation-Kinetics in Amorphous Selenium for Above-Bandgap and Sub-Bandgap Illumination. Applied Physics Letter, 105(5):051912. E-published August 8, 2014.

Mishchenko, A., Lindberg, G.P., Weinstein, B.A., and Reznik, A.



The relaxation of photodarkening (PD) brought about by above-bandgap and sub-bandgap excitations is studied in a wide temperature range in amorphous selenium (a-Se) films designed for avalanche photodetectors.  The experimental results suggest that in contrast to sub-bandgap excitation, above-bandgap excitation does not cause the formation of self-trapped excitons, viz., photoinduced transformation of the a-Se ground state configuration into a metastable higher-energy configuration.  For above-bandgap excitation only transient PD is observed, and its subsequent relaxation can be explained by thermalization and energy relaxation of uncorrelated carriers through the band-tails in order to restore the ground state configuration.  In contrast, sub-bandgap excitation causes both transient and reversible PD, with the latter controlled by the formation of self-trapped excitons, whose relaxation requires overcoming an energy barrier of 0.78 ± 0.02 eV either by thermal activation (at elevated temperatures) or by configurational tunneling (for temperatures below room temperature).

More Articles


Virtual Tour

Check out this 360 degree view of the main research areas in our facilities at ICR Discoveries and Thunder Bay Regional Health Sciences Centre. Learn more about our chemistry and biology labs, and the state of the art characterization lab and clean room.

Take the tour