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Zn‐poor Cu 2 ZnSnSe 4 thin films and solar cell devices
Author(s) -
Fairbrother Andrew,
Neuschitzer Markus,
Saucedo Edgardo,
PérezRodríguez Alejandro
Publication year - 2015
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.201431408
Subject(s) - annealing (glass) , chalcogen , materials science , thin film , stoichiometry , solar cell , photovoltaic system , czts , sputtering , photovoltaics , fabrication , characterization (materials science) , metal , optoelectronics , analytical chemistry (journal) , chemical engineering , nanotechnology , metallurgy , crystallography , chemistry , medicine , ecology , alternative medicine , pathology , engineering , biology , chromatography
This work reports the synthesis of photovoltaic‐grade Cu 2 ZnSnSe 4 thin films with Zn‐poor compositions (Zn/Sn < 1) prepared by selenization of sputter deposited metallic precursors. This contrasts with most other reports where up to now fabrication of photovoltaic‐grade Cu 2 ZnSnSe 4 requires Cu‐poor and Zn‐rich compositions, which often favor the formation the ZnSe secondary phase. Synthesis of Zn‐poor or stoichiometric films opens up prospects for preparing device‐grade films while minimizing formation of common secondary phases. While the maximum device efficiency is modest (2.5%), it is notable because it falls outside the optimum compositional range. Annealing conditions including temperature, chalcogen source, and system pressure were varied to determine their influence on film and device properties. Phase characterization confirms that Cu 2 ZnSnSe 4 is the main phase present. Reasons for the formation of device‐grade films outside the ideal compositional range are discussed, including the fact that initial film growth is under Zn‐rich conditions, and that films are Cu‐poor in relation to Zn (Cu/Zn < 2), both of which may potentially give rise to the necessary electronic defects for a photovoltaic‐grade absorber layer. Finally, the importance reporting other compositional ratios, especially Cu/Zn and Cu/Sn, instead of the more common ratio Cu/(Zn + Sn), is expounded for this class of materials.