Photoelectrochemical Fabrication of CuO-Cu₂O Nanocomposite Semiconductors by High-Frequency Potential-Switching in Copper(II)-Tartrate Complex Aqueous Solution and the Energy Band Structures

Abstract

P-type CuO-Cu2O nanocomposite semiconductors composed of Cu2O-embedded CuO aggregations and Cu2O aggregation consisting of space-filling CuO grains have been fabricated by photoelectrochemical high-frequency potential-switching of 100 to 1000 cycles in an aqueous solution containing copper(II) sulfate hydrate, tartaric acid, and sodium hydroxide, and the size of both the CuO and Cu2O grains decreased from 40-44 nm to approximately 10 nm remaining the characteristic monoclinic and cubic lattices with increase in cycle numbers. The bandgap energy of CuO components was almost a constant value of 1.5 eV, and the Cu2O components showed a decrease in bandgap energy from 2.05 to 1.85 eV with an increase in cycle number due to the Cu2+ state incorporation, and the CuO-Cu2O nanocomposites possessed an ionization energy of approximately 5.2 eV and work function of approximately 4.6 eV, respectively, and were close to those for single CuO and Cu2O layers.

Al:Cu2O n-Type Semiconductors─Electrochemical Fabrication of Heterojunction and Homojunction Photovoltaic Devices

“…12 Other types of photovoltaic structures that satisfy such criterion have been proposed for Cu 2 O/CuO bilayer 13 and Cu 2 O−CuO nanocomposite semiconductors. 14 Si tandem solar cells have attracted increasing attention as a high-performance and lowcost solar cell available for conventional use, 15 types of top cell materials and devices have been explored including the wide-band gap Cu 2 O semiconductor. 16 Cu 2 O is intrinsically a p-type semiconductor with a band gap energy of 2.1 eV, 17 while n-type Cu 2 O semiconductor layers can be prepared by either introducing impurity elements such as Mn and Cl into Cu 2 O layers or electrodeposition in an acidic copper(II)-acetate aqueous solution.…”

“…The inclusion of two or more p-type semiconductors with different band gap energies is an important criterion to overcome the efficiency limit for single solar cells; multijunction solar cells and quantum dots solar cells have been proposed to realize high conversion efficiencies above 30%, − as demonstrated for the conversion efficiencies of 39.7 and 47.0% for the six-junction solar cell at 1 sun and concentrated conditions . Other types of photovoltaic structures that satisfy such criterion have been proposed for Cu 2 O/CuO bilayer and Cu 2 O–CuO nanocomposite semiconductors . Si tandem solar cells have attracted increasing attention as a high-performance and low-cost solar cell available for conventional use, and several types of top cell materials and devices have been explored including the wide-band gap Cu 2 O semiconductor …”