Cation Off-Stoichiometry Leads to High p-Type Conductivity and Enhanced Transparency in Co2ZnO4 and Co2NiO4 Thin Films

Journal Article · Wed Feb 15 00:00:00 EST 2012 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.85.085204· OSTI ID:1045092

Zakutayev, A; Paudel, T R; Ndione, P F; Perkins, J D; Lany, S; Zunger, A; Ginley, D S

We explore the effects of cation off-stoichiometry on structural, electrical, optical, and electronic properties of Co{sub 2}ZnO{sub 4} normal spinel and Co{sub 2}NiO{sub 4} inverse spinel using theoretic and experimental (combinatorial and conventional) techniques, both at thermodynamic equilibrium and in the metastable regime. Theory predicts that nonequilibrium substitution of divalent Zn on nominally trivalent octahedral sites increases net hole density in Co{sub 2}ZnO{sub 4}. Experiment confirms high conductivity and high work function in Co{sub 2}NiO{sub 4} and Zn-rich Co{sub 2}ZnO{sub 4} thin films grown by nonequilibrium physical vapor deposition techniques. High p-type conductivities of Co{sub 2}ZnO{sub 4} (up to 5 S/cm) and Co{sub 2}NiO{sub 4} (up to 204 S/cm) are found over a broad compositional range, they are only weakly sensitive to oxygen partial pressure and quite tolerant to a wide range of processing temperatures. In addition, off-stoichiometry caused by nonequilibrium growth decreases the optical absorption of Co{sub 2}ZnO{sub 4} and Co{sub 2}NiO{sub 4} thin films, although the 500-nm thin films still have rather limited transparency. All these properties as well as high work functions make Co{sub 2}ZnO{sub 4} and Co{sub 2}NiO{sub 4} thin films attractive for technological applications, such as hole transport layers in organic photovoltaic devices or p-type buffer layers in inorganic solar cells.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Science, Basic Energy Sciences, Energy Frontier Research Center for Inverse Design
• DOE Contract Number: AC36-08GO28308
• OSTI ID: 1045092
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 85, Issue 8; Related Information: Article No. 085204
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
BUFFERS
CATIONS
OXYGEN
PARTIAL PRESSURE
PHYSICAL VAPOR DEPOSITION
PROCESSING
SOLAR CELLS
SPINELS
THERMODYNAMICS
THIN FILMS
TRANSPORT
WORK FUNCTIONS
Solar Energy - Photovoltaics
Chemical and Material Sciences