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Registration Number

0221U101555, 0120U104606 , R & D reports

Title

GeSn solid solutions for improved current generation and charge carrier collection in tandem solar cells.

Head

Kondratenko Serhii V., Доктор фізико-математичних наук

Registration Date

22-01-2021

Organization

Taras Shevchenko National University of Kyiv

Description

 GeSn / Ge / Si heterostructures with optimized geometry and morphology of GeSn films have been developed, which show photo response in the middle IR range, and the nature of photoluminescence and photoconductivity in stressed solid solutions of GeSn of different component composition has been established. The morphology of GeSn thin films and their photoelectric properties by atomic force microscopy, kinetic measurements of photocurrent relaxation and photoconductivity spectroscopy have been studied. The mechanisms of recombination of carriers of photoexcited charge carriers in GeSn thin films of different component composition have been studied. A model has been developed that describes the temperature dependence of the charge carriers' lifetime assuming the simultaneous effect of Shockley-Reed-Hall recombination and radiative recombination. It was found that dislocations cause the appearance of a band of electronic states with the highest occupied state with energy EV + (85 ÷ 90) meV, which acts as Shockley-Reed-Hall recombination centers and determines the lifetime of the charge carrier. The application of photoluminescence and photoconductivity spectroscopy methods made it possible to distinguish the contribution of electronic interband transitions and dislocation-related transitions. It is shown that in non - indirect GeSn films deep levels of dislocations cause a shift of the photoluminescence spectra towards lower energies by 80 ± 20 meV relative to the edge of the photoconductivity spectrum. The role of a deeper acceptor level at EV + (140 ÷ 160) meV in the processes of recombination of charge carriers in GeSn films with better structural perfection and Sn content above 4% has been elucidated.

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Datsenko Olexander I.
Kozachenko Viktor V