Synthesis of Zinc Oxide Quantum Dots for Flexible Solar Cell Applications

Economic distress resulting from dependence on diminishing fossil fuels has emphasized the urgent need for new, clean, and efficient fuel sources.  Developments in understanding solar energy, a versatile, renewable resource, have resulted in the production of bio-inspired materials, including solar cells, which harness the power of light to produce energy.  Commercially available solar cells face severe cost, efficiency, and structural limitations, which must be overcome as the energy crisis progresses. Therefore, interest in the use of dye-sensitized solar cell (DSSC) and quantum dot solar cell (QDSC) technologies as lower cost and higher efficiency alternatives have been on the rise. Unfortunately, many existing QDSCs contain cadmium metal, which is banned in many countries due to its toxicity and leachability into aquatic environments. Furthermore, as a means to combat the structural limitations of traditional solar cells, research on conducting polymeric matrices has been a field of expanding interest. This work sought to employ a “green synthetic” route in the preparation of QDSCs with a conductive polymeric (cellulose) matrix as the active substrate. ZnO quantum dots (QD’s) were synthesized in an alkaline aqueous solution under ambient conditions.  The ZnO QD’s were blended with titanium dioxide (TiO₂) nanoparticles in an azeotropic ethanol/water mixture and the resulting dispersion was functionalized with various light absorbing dye molecules. This nanocomposite was combined with the conductive polymer matrix, creating a thin film photoanode for photon capture. The resulting photovoltaic (PV) cell was tested to determine the voltage across the circuit. Current results show that the addition of QDs to the solar cell system results in increased stability as well as a sustainable voltage greater than 50% higher than that of their DSSC counterpart.