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Zn–Ni–Co–O wide-band-gap p-type conductive oxides with high work functions

A. Zakutayeva1 c1, J.D. Perkinsa1, P.A. Parillaa1, N.E. Widjonarkoa2, A.K. Sigdela3, J.J. Berrya4 and D.S. Ginleya4

a1 National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401

a2 National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401; Department of Physics, University of Colorado, Boulder, Colorado 80309

a3 National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, Colorado 80401; Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208

a4 National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, CO 80401

Abstract

Co3O4-based spinels are a new class of wide-band-gap p-type conductive oxides with high work functions. We examined the structures, conductivities, work functions, and optical spectra of quaternary Zn–Ni–Co–O thin films across the entire spinel region of the ZnO–NiO–Co3O4 diagram using a high-throughput combinatorial approach. We found that the conductivity of as-deposited films is maximized (100 S/cm) and optical absorption (at 1.8 eV) is minimized in different regions of the diagram, while the work function of annealed films is high and relatively constant (5.8 ± 0.1 eV). These properties made Zn–Ni–Co–O thin films applicable as p-type interlayers in solar cells. As an example, amorphous Zn–Co–O hole transport layers had good performance in bulk heterojunction organic photovoltaic devices.

(Received June 24 2011)

(Accepted August 04 2011)

Correspondence:

c1 Address all correspondence to A. Zakutayev at andriy.zakutayev@nrel.gov

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