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The Role of Sodium as a Surfactant and Suppressor of Non‐Radiative Recombination at Internal Surfaces in Cu 2 ZnSnS 4
Author(s) -
Gershon Talia,
Shin Byungha,
Bojarczuk Nestor,
Hopstaken Marinus,
Mitzi David B.,
Guha Supratik
Publication year - 2015
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201400849
Subject(s) - czts , materials science , passivation , radiative transfer , grain boundary , photoluminescence , sodium , pulmonary surfactant , non radiative recombination , acceptor , chemical physics , chemical engineering , optoelectronics , nanotechnology , thin film , optics , condensed matter physics , microstructure , composite material , metallurgy , physics , semiconductor , engineering , layer (electronics) , semiconductor materials
It is well‐known that sodium improves the performance of Cu 2 ZnSnS 4 (CZTS) devices, yet the mechanism of the enhancement is still not fully understood. This work aims to present a unified account of the relationships between grain boundaries in CZTS, sodium content at these boundaries, non‐radiative recombination, and surfactant effects that produce large microstructural changes. Using temperature‐dependent photoluminescence measurements, it is demonstrated that samples containing dramatically different grain sizes display identical radiative and non‐radiative decay characteristics when sufficient sodium is present in the film. It is also shown that the sodium concentration needed to efficiently passivate non‐radiative defects is significantly less that the quantity needed to obtain micrometer‐sized CZTS grains. Finally, the high densities of donor‐acceptor pairs that are observed in CZTS films appear to reside within the grains themselves, rather than at grain boundaries.