Synthesis Of Silicon Nanocrystals And Their Application In Solar Cells

Silicon nanocrystals (Si NCs) hold great promise for the development of photovoltaics owing to their remarkable properties enabled by quantum confinement effect and multi-exciton generation effect. The application of Si NCs in photovoltaics may be realized by the fabrication of novel solar cell structures incorporated with Si NCs (Si quantum dot solar cells). However, the ready use of Si NCs in photovoltaics may begin with the coupling of Si NCs with conventional solar cells.A nonthermal plasma system for the synthesis of Si NCs has been successfully set up. With this system Si NCs were produced. The light emission from Si NCs were tuned by changing the size of Si NCs,.About 3 nm Si NCs were dispersed in isopropanol (IPA) to form silicon ink with a concentration of 1 mg/mL. Si-NC films were obtained at the surface of acid-textured monocrystalline silicon solar cells by means of spin coating. Efficiency enhancement up to 3.7% was observed for these silicon solar cells. After air exposure for 11 days, the efficiency enhancement decreased to be 1.4%.Optical simulation was carried out to study the effect of Si-NC films on the light transmission and down-shifting in the wavelength range from 300-1100 nm in both unencapsulated and encapsulated solar cells. In this mode, quantunm yield (QY) of Si NCs is postulated to be 100%; porosity and thickness won't interact with each other. The incident angle varied from 0 to 75 degrees. For unencapsulated solar cells a 30-nm-thick Si-NC film with a porosity of 75% might optimally enhance the solar cell efficiency. For encapsulated solar cells the thickness and porosity of the Si-NC film with maximum enhancement of solar cell efficiency were 30 nm and 65%, respectively.