QUANTUM DOT SOLAR CELL OPTIMIZATION

Copper Sulfide Solar cell on the left. Iodide electrolyte cell on the right.

CdSe Quantum Dot synthesis and isolation

TiO2 layer baking in a furnace

TiO2-cast slides immersed in a quantum dot-dichloromethane solution

TiO2 layer Scanning Electron Microscopy characterization of layer consistency

TiO2 film optical profiler characterization showing 20um thickness

QUANTUM DOT SOLAR CELL OPTIMIZATION AND FABRICATION

Key Skills: Chemical synthesis, MATLAB, solar cell fabrication, QDSC design,

I spearheaded this personal project to design and fabricate a series of 16 optimized quantum dot-solar cells that would maximize solar conversion efficiency. I synthesized 6 batches of CdSe quantum dot solutions with aliquots differing by a maximum of 20nm in wavelength. I collected spectroscopy data and calculated the transition energy, extinction coefficient, and particle size for all aliquots. I synthesized a 20um TiO2 mesoscopic oxide film and characterized it using an optical microscope, an optical profiler, and with Scanning Electron Microscopy (SEM). For every solar cell, I collected data on the potential output under darkness, ambient light, and luminescence of 765 lux. I additionally calculated the current-voltage curve, open circuit voltage, short circuit current, maximum power, fill factor, and cell efficiency.

I constructed each solar cell with varying parameters such as: electrolyte couple (iodide vs polysulfide), counterelectrode (graphite vs silver vs copper sulfide), blocking layer (zinc sulfide vs none), scattering layer (TiO2 vs none), and QD deposition methods.

Additionally, I simulated 3 MATLAB theoretical models. One model quantifies the optimal TiO2 layer thickness by using a Boltzmann distribution to model flow of electrons through the layer as a random walk and by simulating the Brownian forces experienced by electrons. The other model captures the distribution of electron displacement in the TiO2 layer and simulates the effect of a blocking layer, therefore quantifying the percentage of electrons which are protected from back electron flow. The final model uses real solar data to calculate the Shockley-Queisser Limit.

Remarkable Achievements:

Of the 16 solar cells:

1 exhibited fascinating behavior, consistently producing high voltages in darkness but 0 volts under light
3 had voltage outputs up to 10 times greater than predicted
3 behaved very oddly, producing their highest voltages under ambient light
5 behaved as expected
4 were unresponsive to lighting

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