The document summarizes research into using different surface morphologies of cuprous oxide (Cu2O) nanocrystals for solar cell applications. Nanocubes and nanooctahedrons were synthesized and characterized. Photoelectrochemical tests found that nanooctahedrons had increased photocatalytic activity and stability over nanocubes. Both nanocrystal types showed higher external quantum efficiency and solar cell efficiency than silicon-based cells. The results indicate that controlling nanocrystal morphology can optimize materials for inexpensive and efficient solar technologies.

1. Effects of surface morphology on
enhanced photoelectrochemical
properties of nanocrystals
Elizabeth Donoway

2. Solar Technology
• Current silicon-based solar panels
• Expensive
• Inefficient
• Prone to damage
• Silicon sheeted panels
• Unstable
• Large band gap
• Low energy output
• Small surface area
Gupta, S. et al., 2013

3. Nanocrystals
• Larger surface area to volume ratio
• Regulated manipulation of characteristics
• Unique electrochemical properties
• Multi-faceted nanocrystals
• Configuration and structure determine stability
• {100}-bound cubes
• {111}-bound octahedrons
Yang, Y. et al., Nanoscale, 2014, 6, 4316

4. New Solar Materials
• Cuprous oxide (Cu2O)
• Efficient
• Inexpensive
• Small band gap
• Unstable
• Polyvinylpyrrolidone (PVP)
• Capping molecule
• Stabilization of crystals
Zhang, D. F. et al., Journal of Materials Chemistry, 2009, 19(29), 5220-5225.
Van de Krol, R. et al., Journal of Materials
Chemistry, 2008, 18(20), 2311-2320

5. Purpose
• Determine the effects of surface morphology on
nanocrystal stability
• Fabricate Cu2O nanocrystals that are stable in solution
• Optimize nanocrystal morphology to create efficient
materials for use in solar reactions

6. Methods
• Nanocrystal Synthesis
• Seeding of crystals from copper (II) chloride
• Addition of PVP to form octahedrons by truncating cube vertices
• Characterization
• TEM/SEM Imaging
• Electrode Preparation
• Adhesion of nanocrystals to FTO glass slides
• Photoelectrochemical Assays
• Controlled Potential Electrolysis (CPE)
• Determines electrode stability
• External Quantum Efficiency (EQE)
• Determines wavelengths of light that the solar panel is optimized for
use in
• Solar Cell Efficiency
•

7. Results – Characterization
Cu2O Nanocubes
Cu2O Nanooctahdrons
Cu2O Nanocubes
Cu2O Nanooctahedrons

8. Results – Characterization
• Both nanocubes and nanocrystals were successfully
fabricated
• TEM/SEM imaging confirmed that sizes and shapes of
nanocrystals were differentiated, preventing agglomeration
and sheeting, which would lower efficiency and reduce
surface area available for light reactions to occur

9. Results – Controlled Potential
Electrolysis (Nanocubes)
Single deposition of Cu2O nanocubes on FTO glass (average of 40 trials). CPE was conducted at
increased energies equivalent to those exposed over a typical solar panel lifetime, corresponding
to decades of solar cell use. Electrode samples were irradiated with solar light during two five-
minute periods, alternating light and dark conditions in five second intervals.
Dark DarkLight Light

10. Results – Controlled Potential
Electrolysis (Nanocubes)
Single deposition of Cu2O nanocubes on FTO glass during light irradiation intervals.
Light and dark conditions were alternated in five second intervals to ensure that
electrodes remained stable during large fluctuations in photonic energy. Baseline
photocurrent density (J) remained constant between solar irradiation periods during
electrolysis. The obtention of photocurrent density away from the zero value during
light irradiation over all 40 trials indicated maintained stability of electrodes.
Light on
Light off

11. Results – Controlled Potential
Electrolysis (Nanooctahedrons)
Single deposition of Cu2O nanooctahedrons on FTO glass (average of 40 trials). Electrode samples were
irradiated with solar light during two five-minute periods, alternating light and dark conditions in five
second intervals. Exponential increase in magnitude of photocurrent density during light conditions
indicates increased photocatalytic activity in nanooctahedron electrodes.
Light LightDarkDark

12. Results – Controlled Potential
Electrolysis (Nanooctahedrons)
Single deposition of Cu2O nanooctahedrons on FTO glass. Baseline remained
constant between solar irradiation periods during electrolysis. Increase in
photocurrent density magnitude away from the zero in all trials indicates
maintained stability and increased photocatalytic response.
Light off
Light on

13. Results – External Quantum
Efficiency
External quantum efficiency expressed as a percentage of photons absorbed and converted into
electric current, modeled as a function of wavelength (nm). The longer range of wavelengths for
which both Cu2O nanocrystal panels achieve 100% external quantum efficiency compared to Si-
based cells indicates their optimization for use in the solar emission spectrum.
[ ]
Si-based

14. Results – Solar Cell Efficiency
• Cu2O Electrode Efficiency
• ηmax,theoretical =86%
• Cu2O Nanocube Efficiency
• Pmax=107.2 mW
• ηexperimental=53.6%
• Cu2O Nanooctahedron Efficiency
• Pmax=125.4 mW
• ηexperimental=62.7%
• Silicon Panel Efficiency
• ηmax,theoretical=29%
• ηmax,experimental=21.5%

15. Discussion
• Stability
• Stabilization of Cu2O via morphological manipulation of
nanocrystals
• Both nanocubes and nanooctahedrons remained stable
• Photocurrent density magnitude increase in light condition
• 11 μA cm-2 difference in magnitude between octahedron and cube
electrodes
• Efficiency
• Nanocrystals optimized for use in solar emission spectrum
• Different morphologies demonstrate varied electrochemical
properties
• Nearly 200% increase in efficiency over Si-based cells
• Applications
• Addresses instability of current materials
• New, inexpensive solar technologies made from Cu2O
• Cu2O cells are half as expensive to produce as Si-based cells

16. Future Research
• Assessment of photovoltaic cell performance and
resistance to degradation under environmental conditions
• More specific evaluation of nanooctahedron morphology to
further optimize nanocrystals for use in solar panels and
increase panel efficiency
• Stabilization of alternate materials (e.g. graphene,
germanium arsenide, titanium dioxide) for use in solar
panels

17. Acknowledgements
• Joseph DuChene
• Dr. Wei David Wei
• Wei Research Group
• Student Science Training Program
• Pine Crest School
• Sigma Xi

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