Exciton photoluminescence and benign defect complex formation in zinc tin nitride

Emerging photovoltaic materials need to prove their viability by demonstrating excellent electronic properties. In ternary and multinary semiconductors, disorder and off-stoichiometry often cause defects that limit the potential for high-efficiency solar cells. Here we report on Zn-rich ZnSnN 2 (Zn/...

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Bibliographic Details
Published in:Materials horizons 2018-01, Vol.5 (5), p.823-830
Main Authors: Fioretti, Angela N., Pan, Jie, Ortiz, Brenden R., Melamed, Celeste L., Dippo, Patricia C., Schelhas, Laura T., Perkins, John D., Kuciauskas, Darius, Lany, Stephan, Zakutayev, Andriy, Toberer, Eric S., Tamboli, Adele C.
Format: Article
Language:English
Subjects:
Annealing
Atomic structure
Complex formation
Computer simulation
Defects
Donors (electronic)
Electronic properties
Electronic structure
exciton photoluminescence
Excitons
First principles
MATERIALS SCIENCE
Monte Carlo simulation
Photoluminescence
Photovoltaic cells
photovoltaic materials
Solar cells
SOLAR ENERGY
Stoichiometry
Tin
Titanium nitride
Viability
X-ray diffraction
Zinc
zinc tin nitride
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Summary:Emerging photovoltaic materials need to prove their viability by demonstrating excellent electronic properties. In ternary and multinary semiconductors, disorder and off-stoichiometry often cause defects that limit the potential for high-efficiency solar cells. Here we report on Zn-rich ZnSnN 2 (Zn/(Zn + Sn) = 0.67) photoluminescence, high-resolution X-ray diffraction, and electronic structure calculations based on Monte-Carlo structural models. The mutual compensation of Zn excess and O incorporation affords a desirable reduction of the otherwise degenerate n-type doping, but also leads to a strongly off-stoichiometric and disordered atomic structure. It is therefore remarkable that we observe only near-edge photoluminescence from well-resolved excitons and shallow donors and acceptors. Based on first principles calculations, this result is explained by the mutual passivation of Zn Sn and O N defects that renders both electronically benign. The calculated bandgaps range between 1.4 and 1.8 eV, depending on the degree of non-equilibrium disorder. The experimentally determined value of 1.5 eV in post-deposition annealed samples falls within this interval, indicating that further bandgap engineering by disorder control should be feasible via appropriate annealing protocols.
ISSN:2051-6347
2051-6355
DOI:10.1039/C8MH00415C