Journal
MATERIALS HORIZONS
Volume 5, Issue 5, Pages -Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c8mh00415c
Keywords
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Funding
- U.S. Department of Energy's (DOE) Office of Energy Efficiency and Renewable Energy (EERE) under Solar Energy Technologies Office (SETO) [30302]
- EERE
- DOE's Office of Science (SC), Basic Energy Sciences (BES) [DE-AC02-76SF00515]
- DOE-SC-BES, Materials Sciences and Engineering Division
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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 ZnSnN2 (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.
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