Solar cells based on cadmium tellurium thin film and composite of orgamic and inorganic nano-scale materials.

摘要

In recent years there has been much interest in solar energy conversion because of oil price hike and environmental issues of burning fossil fuels. Photovoltaic solar cells are a promising alternative energy source. In this work, to start with, CdTe solar cells were fabricated and tested. CdTe was grown by e-beam evaporation followed by post annealing. 12% energy conversion efficiency achieved with first efforts. To explore materials for tandem solar cells, nanowires were studied. PbSe nanowires were grown by magnetron sputtering, and its crystal structure and stoichiometry as well as its optical properties were characterized. Closely packed PbSe nanowires with diameters of approximately 100 nm were grown. In spite of their relatively large size these wires showed a large blue shift in the luminescence and absorption and hence of its energy band gap compared to the bulk crystal demonstrating quantum confinement. This has been attributed to pinning of the Fermi level due to surface states, band bending and a strong depletion layer witch confines the carrier states. PbSe nanowires with different diameters are promising candidate for a new tandem cell. We also investigated enhancement of light harvesting in photosynthesis by integration of nanocrystalline (NQDs) quantum dots and photosystem I (PSI). We show strong evidence of energy transfer from CdSe NQDs to PSI by PL and transient absorption measurements. Experimental data indicates that the energy of the excited charge carriers in CdSe NQDs were transferred to PSI by means of radiative emission, FRET, and electron/hole transfer between inorganic/organic system. This exciting breakthrough provides a basis for design of novel energy harvesting and other electronic devices based on photosynthesis. Applying tandem structure and incorporating nanostructures paths exist toward solar cells with higher efficiency.