Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster Session I

HL 13.39: Poster

Monday, March 12, 2018, 17:30–19:30, Poster B

Charge Carriers Dynamics in Kesterite: From Ultra-fast Trapping via Localized Transport to Surface Recombination — •Hannes Hempel, Rainer Eichberger, and Thomas Unold — Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner Platz 1, 14109 Berlin

Kesterite solar cells materials are known to exhibit band tails originating from potential fluctuations and defect bands. We investigate how these tails affect the dynamics of photo-excited charge carrier by applying transient absorption and time resolved THz spectroscopy to coevaporated Cu2ZnSnSe4 thin films. We find that 100 fs after excitation with 1.5 eV photons the carriers form a hot Boltzmann distribution in the band states. Within 2 ps they thermalize to lattice temperature and reach simultaneously band edge and tail states. Afterwards the carriers are distributed in bands, tails and defects and exhibit in average a localized mobility with a DC-value of 100 cm2/Vs. Their transport can be described by a sequence of trapping and detrapping between extended band and localized tail states.