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Multiple Exciton Generation in SiGe Nanoclusters: A Numerical Study
Author(s) -
Gordi Mahdi,
MoravvejFarshi Mohammad K.
Publication year - 2018
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201800407
Subject(s) - nanoclusters , molar absorptivity , exciton , absorption (acoustics) , cluster (spacecraft) , materials science , band gap , molecular physics , atomic physics , physics , optoelectronics , condensed matter physics , optics , nanotechnology , computer science , programming language
The multiple exciton generation (MEG) in Si (0≤ x ≤7) Ge (7− x ) nanoclusters using the equation‐of‐motion coupled‐cluster (EOM‐CCSD) method has been studied here. Simulation results indicate that the energy normalized to the optical bandgap, at which the absorptivity profile peaks, depends on the elemental structure of the nanocluster (NC). Moreover, the results show that the larger the number of Si atoms ( x ) in the NC, the larger the normalized MEG threshold to the optical energy gap ( E Th ), and the larger the optical absorption cross section. As an example, the maximum absorptivity in Si 7 Ge 0 nanocluster is about 2.37 times that in Si 0 Ge 7 , and E Th for the former NC is larger than that of the latter. Hence, the superior optical absorptivity of Si 7 shows, despite its larger normalized MEG threshold, it is the most desirable option for the MEG process in light‐harvesting devices, including solar cells. This is contrary to the concluding remark in our previous study that was made solely on the basis of comparing the normalized MEG thresholds.