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Dynamic Impurity Redistributions in Kesterite Absorbers
Author(s) -
Grini Sigbjørn,
Aboulfadl Hisham,
Ross Nils,
Persson Clas,
Platzer-Björkman Charlotte,
Thuvander Mattias,
Vines Lasse
Publication year - 2020
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.202000062
Subject(s) - impurity , materials science , annealing (glass) , hydrogen , agglomerate , crystallite , secondary ion mass spectrometry , oxygen , analytical chemistry (journal) , kesterite , crystallization , chemical engineering , thin film , chemistry , nanotechnology , mass spectrometry , metallurgy , composite material , chromatography , organic chemistry , czts , engineering
Cu 2 ZnSn(S,Se) 4 is a promising nontoxic earth‐abundant solar cell absorber. To optimize the thin films for solar cell device performance, postdeposition treatments at temperatures below the crystallization temperature are normally performed, which alter the surface and bulk properties. The polycrystalline thin films contain relatively high concentrations of impurities, such as sodium, oxygen and hydrogen. During the treatments, these impurities migrate and likely agglomerate at lattice defects or interfaces. Herein, impurity redistribution after air annealing for temperatures up to 200 °C and short heavy water treatments are studied. In addition, nonuniformities of the sodium distribution on a nanometer and micrometer scale are characterized by atom probe tomography and secondary ion mass spectrometry, respectively. Sodium and oxygen correlate to a greater extent after heat treatments, supporting strong binding between the two impurities. Redistributions of these impurities occur even at room temperature over longer time periods. Heavy water treatments confirm out‐diffusion of sodium with more incorporation of oxygen and hydrogen. It is observed that the increased hydrogen content does not originate from the heavy water. The existence of an “ice‐like” layer on top of the Cu 2 ZnSnS 4 layer is proposed.