Dresden 2014 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 81: Poster: Energy materials incl. photovoltaics
HL 81.5: Poster
Mittwoch, 2. April 2014, 17:00–20:00, P1
Nanoparticles with high pressure core structures and Si-ZnS nanocomposites: New Paradigms to Improve the Efficiency of MEG Solar Cells — •Stefan Wippermann1, Marton Vörös2, Balint Somogyi3, Adam Gali3, Dario Rocca4, Francois Gygi2, Gergely Zimanyi2, and Giulia Galli2 — 1Max-Planck-Institute for Iron Research, Düsseldorf — 2University of California, Davis — 3Budapest University of Technology and Economics — 4Universite de Lorraine, Nancy
The efficiency of nanoparticle (NP) solar cells may substantially exceed the Shockley-Queisser limit by exploiting multi-exciton generation. However, (i) quantum confinement tends to increase the electronic gap and thus the MEG threshold beyond the solar spectrum and (ii) charge extraction through NP networks may be hindered by facile recombination. Using ab initio calculations we found that (i) Si and Ge NPs with exotic core structures such as BC8 exhibit significantly lower gaps and MEG thresholds than particles with diamond cores, and an order of magnitude higher MEG rates. (ii) We also investigated Si NPs embedded in a ZnS host matrix and observed complementary charge transport networks, where electron transport occurs by hopping between NPs and hole transport through the ZnS-matrix. Such complementary pathways may substantially reduce recombination, as was indeed observed in recent experiments. We employed several levels of theory, including DFT with hybrid functionals and GW calculations.