BS in Materials Engineering
Materials Engineering Department
Solar cells have been found to absorb light more efficiently and effectively when the energy of incoming photons matches the electronic band gap of the solar cell. Spectral conversion of light from UV to lower energy wavelengths can improve solar cell efficiency an estimated 14.5%. Cadmium Selenium/Zinc Sulfide Core/Shell quantum dots have been successfully embedded in PDMS silicone elastomer. Using a Keithley 2400 Electrometer with Labview software, voltage and current characteristics have been recorded in steps of 10 mV with a wait time of 250 ms on a commercially available solar cell using an artificial solar spectrum created by a Tungsten Halogen lamp. The commercially available solar cell was found to have a maximum power output of 250 mW and a fill factor of 71.025%. Short term repeatability testing and long term reproducibility testing was conducted using a sample size of ten and a wait time of 1 hour and 1 day respectively, repeated five times. The system was found to have a long term reproducibility of 0.010% and a short term repeatability of 0.004% after a one hour warm-up period to reach a thermal equilibrium. Three mechanisms of light attenuation have been observed due to PDMS: the addition of interfaces, surface adhesion, and thickness. The most substantial loss was created by the addition of interfaces which decreased the fill factor of the solar cell by 0.00839 or 1.18%. Losses from surface adhesion and losses due to increasing thickness were minimal. The CdSe/ZnS core/shell quantum dots used fluoresced at a wavelength of 570 nm. These quantum dots were dried from octadecane and then suspended in toluene before being mixed with bulk PDMS to create the spectral converter. The spectral converter increased short circuit current by 1% and did not change open circuit voltage or fill factor. The maximum power was increased to be equal to that of the bare solar cell.