15 October 2015 Contrastive analysis of multiple exciton generation theories
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Proceedings Volume 9671, AOPC 2015: Advances in Laser Technology and Applications; 96710I (2015) https://doi.org/10.1117/12.2199053
Event: Applied Optics and Photonics China (AOPC2015), 2015, Beijing, China
Multiple exciton generation (MEG) is an effect that semiconductor nanocrystals (NCs) quantum dots (QDs) generate multiple excitons (electron-hole pairs) through absorbing a single high energy photon. It can translate the excess photon energy of bandgap (Eg) into new excitons instead of heat loss and improve the photovoltaic performance of solar cells. However, the theories of MEG are not uniform. The main MEG theories can be divided into three types. The first is impact ionization. It explains MEG through a conventional way that a photogenerated exciton becomes multiple excitons by Coulomb interactions between carriers. The Second is coherent superposition of excitonic states. Multiple excitons are generated by the coherent superposition of single photogenerated exciton state with enough excess momentum and the two-exciton state with the same momentum. The third is excitation via virtual excitonic states. The nanocrystals vacuum generates a virtual biexciton by coulomb coupling between two valence band electrons. The virtual biexciton absorbing a photon with an intraband optical transition is converted into a real biexciton. This paper describes the MEG influence on solar photoelectric conversion efficiency, concludes and analyzes the fundamentals of different MEG theories, the MEG experimental measure, their merits and demerits, calculation methods of generation efficiency.
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Hengyu Tan, Hengyu Tan, Qing Chang, Qing Chang, } "Contrastive analysis of multiple exciton generation theories", Proc. SPIE 9671, AOPC 2015: Advances in Laser Technology and Applications, 96710I (15 October 2015); doi: 10.1117/12.2199053; https://doi.org/10.1117/12.2199053

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