Thin Film of Silicon Quantum Dots : Synthesis and Characterizations for Potential Device Applications

In achieving high efficiency solar cells at low production cost (i.e. third generation solar cells), significant attempts have been made by several researchers on the evolution of new technologies and materials. In that direction the tandem structure solar cell can boost the efficiency progressively by stacking more cells on top of one another with the utilization of the extended solar spectrum. The band gaps for the each absorber layer will be in the decreasing order from the top cell to the bottom one, in order to absorb the photon in the efficient way. Apart from tandem cells, a number of more ‘paralleled’ approaches have also been suggested capable of similar efficiency to an infinite stack of tandem cells e.g. hot-carrier solar cell. The principal concept underlying the hot carrier solar cell is to slow the rate of photoexcited carrier cooling to allow time for the carriers to be collected whilst they are still at elevated energies (‘hot’), and thus allowing higher voltages to be achieved from the cell. To achieve all-silicon third generation solar cells, the most appropriate way is taking the advantage of quantum confinement effect of the silicon quantum dot which is capable of fine-tuning the optical band gap without compromising the suitable electrical conductivity and the appropriate combination of optical band gap and electrical conductivity is the prerequisite for the different layers of solar cells. Accordingly, this presentation will deal with the development of silicon nano-crystals and quantum dots embedded within the superlattice structures and amorphous matrix of a-SiC and a-SiOx, specifically through chemical vapor deposition and rf-magnetron sputtering at a comparatively low-temperature, compatible for fabrication of different layers of the all silicon solar cells with third generation technology.