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More Se Vacancies in Sb 2 Se 3 under Se‐Rich Conditions: An Abnormal Behavior Induced by Defect‐Correlation in Compensated Compound Semiconductors
Author(s) -
Huang Menglin,
Cai Zenghua,
Wang Shanshan,
Gong XinGao,
Wei SuHuai,
Chen Shiyou
Publication year - 2021
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202102429
Subject(s) - vacancy defect , materials science , semiconductor , fermi level , selenium , compound semiconductor , ionization energy , ionization , crystallographic defect , density functional theory , acceptor , condensed matter physics , chemistry , crystallography , computational chemistry , nanotechnology , ion , optoelectronics , physics , metallurgy , electron , organic chemistry , quantum mechanics , epitaxy , layer (electronics)
It was believed that the Se‐rich synthesis condition can suppress the formation of deep‐level donor defect V Se (selenium vacancy) in Sb 2 Se 3 and is thus critical for fabricating high‐efficiency Sb 2 Se 3 solar cells. However, here it is shown that by first‐principles calculations the density of V Se increases unexpectedly to 10 16 cm −3 when the Se chemical potential increases, so Se‐rich condition promotes rather than suppresses the formation of V Se . Therefore, high density of V Se is thermodynamically inevitable, no matter under Se‐poor or Se‐rich conditions. This abnormal behavior can be explained by a physical concept “defect‐correlation”, i.e., when donor and acceptor defects compensate each other, all defects become correlated with each other due to the formation energy dependence on Fermi level which is determined by densities of all ionized defects. In quasi‐1D Sb 2 Se 3 , there are many defects and the complicated defect‐correlation can give rise to abnormal behaviors, e.g., lowering Fermi level and thus decreasing the formation energy of ionized donor V Se 2+ in Se‐rich Sb 2 Se 3 . Such behavior exists also in Sb 2 S 3 . It explains the recent experiments that the extremely Se‐rich condition causes the efficiency drop of Sb 2 Se 3 solar cells, and demonstrates that the common chemical intuition and defect engineering strategies may be invalid in compensated semiconductors.