Reduced Graphene Oxide Composite Counter Electrode for Quantum Dot Solar Cells

2 J. Phys. Chem. Lett., 2011, 2 (19), pp 2453–2460 DOI: 10.1021/jz201064kNotre Dame Radiation LaboratoryDepartment of Chemical and Biomolecular Engineering1Deparment of Chemistry and Biochemistry2University of Notre Dame, Notre Dame, IN 46556

Motivation•Cu2S exhibits exceptional redoxactivity in aqueous polysulfidesolutions1•Brass is a commonly used counterelectrode in laboratory assessmentsbut degrades over time•Reduced graphene oxide (RGO) isa high surface area, conductivesubstrate with good electronshuttling capability 1. Hodes, G., Manassen, J, J.Electrochem.Sci., 1980

SynthesisSynthetic Steps:1. Complexation of Cu+ with graphene oxide (GO)2. Disproportionation of Cu+ to Cu2+ and Cu03. Wash via centrifugation to remove dissolved Cu2+4. Reduce GO-Cu0 composite to form RGO-Cu05. Add binder and blade onto substrate RGO-Cu2S6. Immerse in polysulfide for conversion of Cu0 to Cu2S Electrode

Characterization Cu S•Good coverage of RGO with Cu2S is observed•Unique characteristics of RGO generate 3-D macrostructure

Electrochemical Response 8 30 Platinum A 6 Cycle 1 RGO-Cu2S B RGO-Cu2S Cycle 2 Current Density (mA/cm ) Current Density (mA/cm ) 2 2 20 4 Cycle 3 10 Cycle 4 2 Cycle 5 0 0 -10 -2 -20 -4 -30 -6 1M Na2S 0.1M Na2S -8 -40 1M S 0.1M S -10 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 Voltage (V vs. SCE) Voltage (V vs. SCE) 500 1.2 Cycle 1 Platinum C Platinum D 1.0 Current Density (mA/cm ) Cycle 2 400 2 0.8 Cycle 3 0.6 Cycle 4 300 Cycle 5 Z (ohm) 0.4 1.00 0.2 200 RGO-Cu2S 0.75 0.0 Z (ohm) -0.2 100 0.50 -0.4 0.1M Na2S 0.25 0.1M S 0 8 10 12 14 -0.6 Z (ohm) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0 200 400 600 800 1000 1200 Voltage (V vs. SCE) Z (ohm)•Pt shows irreversibility and sluggish kinetics with high Rct•RGO-Cu2S reversible response with Nerstian shifts in CVand low Rct corresponding to Jo = 16 mA/cm2

Photoelectrochemical ResponseSuperior electrochemical response with good substrate contact led to fullyregenerative efficiency of 4.4%

Summary•Anchored Cu0 nanoparticles on graphene oxide via disproportionation ofCu+ in ethanol to generate RGO-Cu2S composite•RGO-Cu2S composite exhibits superior regenerative redox activity withpolysulfide without corrosion•High exchange current density leads to lower polarization of counterelectrode and thus higher fill factor and maximum power of the quantumdot solar cell

Thank You! This work can be found in the Journal of Physical Chemistry Letters J. Phys. Chem. Lett., 2011, 2 (19), pp 2453–2460 DOI: 10.1021/jz201064kMore information on the Kamat Research Group can be found at: www.kamatlab.com

Reduced Graphene Oxide Composite Counter Electrode for Quantum Dot Solar Cells

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