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Germanium Incorporation in Cu 2 ZnSnS 4 and Formation of a Sn–Ge Gradient
Author(s) -
Saini Nishant,
Larsen Jes K.,
Sopiha Kostiantyn V.,
Keller Jan,
Ross Nils,
Platzer-Björkman Charlotte
Publication year - 2019
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900492
Subject(s) - czts , crystallinity , materials science , wurtzite crystal structure , sputtering , germanium , grain growth , tin , recrystallization (geology) , grain size , chemical engineering , crystallography , analytical chemistry (journal) , mineralogy , metallurgy , zinc , nanotechnology , thin film , chemistry , composite material , geology , paleontology , silicon , engineering , chromatography
Alloying of Cu 2 ZnSnS 4 (CZTS) with Ge can potentially promote grain growth and suppress the formation of Sn‐related defects. Herein, a two‐step fabrication route based on compound co‐sputtering and sulfurization at a high temperature is used to prepare Ge‐incorporated CZTS (Cu 2 ZnGe x Sn 1 − x S 4 [CZGTS]). For Cu 2 ZnGeS 4 (CZGS), films deposited using elemental Ge and binary GeS targets are compared. The recrystallization is shown to be promoted for the absorbers deposited using Ge target, possibly due to lower sulfur content in the precursor suppressing the formation of wurtzite‐like phases during sputtering. The grain growth and crystallinity in CZGTS are slightly improved for x = 0.2 but not for higher concentration of the incorporated Ge. Owing to the composition‐dependent electronic properties, compositionally graded CZGTS films may be beneficial for reducing recombination towards the back contact. Hence, herein, the successful formation of a steep concentration gradient with Ge and Sn is demonstrated by the deposition of a CZGS/CZTS precursor stack followed by sulfurization with varying time periods.