Metal Sulfide for Quantum Dot-Sensitized Solar Cells and Supercapacitors
Date Issued
2011
Date
2011
Author(s)
Chen, Chia-ying
Abstract
In this thesis, I synthesized nanomaterials for fabrication of counter electrodes of quantum dot-sensitized solar cells (QDSSCs) and supercapacitors (SCs). Through a chemical bath deposition (CBD), Cu(NO3)2 and Na2S were used for the preparation of highly efficient CuS electrodes on transparent fluorine-doped tin oxide glass substrates. Varying the number of CBD cycles allowed us to obtain different types of CuS structures—namely particles, aggregates, ribbon-like structures, and belt-like structures after one, five, seven, and 15 CBD cycles, respectively. I used UV–Vis absorption spectroscopy and scanning electron microscopy to monitor the structural evolution of these CuS structures. Current–potential, electrochemical impedance, and reflectance measurements revealed that the CuS electrodes prepared after seven CBD cycles exhibited high electrocatalytic activity, high reflectivity, and low charge-transfer resistance. Under one-sun illumination (100 mW cm–2), five CdS/CdZnSe quantum dot–sensitized solar cells (QDSSCs) each featuring a CuS electrode prepared from seven CBD cycles provided maximum power conversion efficiencies of 4.71 ± 0.09%. Relative to Pt electrodes, these low-cost CuS electrodes exhibit great electrocatalytic activities, high reflectivity, low charge-transfer resistance, and excellent tolerance toward poisoning in the presence of polysulfide electrolytes. I also prepared carbon nanotubes (CNTs)/CoS nanomaterials (NMs) electrodes by depositing CNTs/CoS NMs onto fluorine-doped tin oxide glass substrates, which function as working electrodes in supercapacitors (SCs). Thermal annealing of CNTs/CoS NMs leads to the crystalline structure evolution. Evidences are supported by the measurements of Raman spectra, X-ray photoelectron spectroscopy and d-spacing. Cyclic voltammograms analysis revealed thermal oxidizing CNTs/CoS NMs electrodes exhibiting excellent electrochemical capacity than that of unannealing CNTs/CoS NMs electrodes. The values of specific capacitance over 1000 and 2000 Fg-1 were obtained at a scan rate of 100 and 10 mV s-1, respectively. To our best knowledge, it is, for the first time, demonstrated the use of annealing CNTs/CoS NMs as great promising high-rate and high efficient SCs.
Subjects
CuS nanostructures
charge-transfer resistance
reflectance
electrocatalytic activity
quantum dot–sensitized solar cells
supercapacitor
cobalt sulfide
nanomaterials
carbon nanotubes
Type
thesis
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