No abstract

Perovskite solar cells, specifically using SnO2 nanoparticles, have been extensively researched and are proving to be extremely promising in the field of renewable energy by increasing a solar cell's overall efficiency and lowering the cost of production. In this study, an experiment was performed to synthesize SnO2 nanoparticles over 8 days. Day 1 was the synthesis which included the mixing of water, tin (II) chloride, methanol, sodium carbonate and dimethylformamide and then heated in a water bath at 28 . Sampling of this solution started on day 4 of the experiment when sufficient particle growth was observed and stopped at day 8. Centrifuging, freezing, and freezedrying were used for each sample to isolate the solid product. Transmission electron microscopy and X-ray powder diffraction was used to characterize the isolated nanoparticle. The results from the X-ray powder diffraction showed that each sample consisted of SnO2 nanoparticles of different sizes. From the transmission electron microscopy on the samples showed that the overall size of the nanoparticles gradually increased during each additional synthesis day.

In dye-sensitized solar cells, it has been observed that dyes have a higher affinity for anatase TiO2 nanoparticles in photoelectrodes. It has also been shown that having the TiO2 semiconductor layer in the solar cell allows for more favorable electron transport. Therefore, having a layer(s) of anatase TiO2 nanoparticles in a solar cell will increase the charge separation efficiency of the device. While a great amount of research has been done on the creation of TiO2 nanoparticles and their effect on the efficiency of dye-sensitized solar cells, not much is known of the effects of low-temperature synthesis of semiconductor TiO2 nanoparticles on these solar cells. In addition, most methods of producing anatase TiO2 nanoparticles require the use of a hightemperature oven for the purpose of a hydrothermal reaction. The purpose of this research is to discover a method of obtaining porous TiO2 semiconductor films comprised of anatase TiO2 nanocrystals using lowtemperature synthesis of TiO2 without hydrothermal reactions of the TiO2 nanoparticles and to observe their characteristics. The TiO2 semiconductor nanoparticles were synthesized at 40 𝑪 𝒐 using TiCl4 and dimethylformamide in an aqueous solution. A method of creating a reaction mixture to produce the semiconductor nanoparticles was slightly varied four times, and the results of each trial were investigated. This method involved the creation of the TiO2 nanoparticles through a low-temperature reaction and dry-freezing the nanoparticles to remove moisture and produce a powder that could be resuspended. Once the TiO2 nanoparticles were obtained using each method, their characteristics, including size and shape, were observed under a transmission electron microscope and X-ray diffraction.

TiO2 nanoparticles are often used as a photoanode material in dye-sensitized solar cells. Sintered together, the TiO2 particles are often conducted at 500℃, to provide porous TiO2 thin films. Anatase TiO2 nanoparticles with the dimensions of around 20-30 nm are routinely used to facilitate better electron transport and high dye-adsorption capacity in the film. Prior experiments on the solution synthesis of TiO2 suggested that dimethylformamide (DMF) plays a crucial role in the formation of DMF-containing amorphous TiO2 precursors in solution, adaptable for creating size-controlled TiO2 nanoparticles in the following high temperature process. It was observed that subsequent sintering process of the precursor at 500℃ produced Anatase TiO2 nanoparticles with the sizes of around 20 nm. The purpose of this research is to discover a method of obtaining Anatase TiO2 semiconductor nanocrystals using low-temperature process without using a high temperature oven. The amorphous TiO2 precursors were prepared at 40℃ using an aqueous TiCl4 solution as a Titanium compound and DMF as a structure directing agent. A new method involved the creation of the semiconductor nanoparticles through freeze-dry the resultant TiO2 antecedents in order to produce a crystalline powder. The size, shape and crystal phase of TiO2 particles were also characterized using a transmission electron microscope (TEM) and X-ray diffraction (XRD). It was found that Anatase nanoparticles formed with freeze-dry process of amorphous TiO2 precursors. This allowed us to produce crystalline TiO2 at a low temperature.

Design of semiconductor SnO2 nanomaterials have gained considerable attention owing to their intriguing performance of electron transport in halide perovskite solar cells (PSC). The purpose of this paper is to investigate the different preparation methods of semiconductor SnO2 films as electron transport layers for PSC. Particular focus is paid to the preparation and characteristics of the SnO2 particles/films in order to understand the relationship between the quality of nanostructured SnO2 films and performance of solar cells. One of the major approaches to obtain SnO2 layers has been the spin-coating deposition of SnO2 nanofluids, made by the surface modification of SnO2 nano-colloids. The preparation of SnO2 nanoparticles using Tin(IV) salts has also been reported to produce a smooth SnO2 film. Light-to-electricity conversion efficiency of near 20% has been reported in several reports on PSC. The advantage of using SnO2 materials includes its superior conductivity, which is much higher than TiO2. This paper also presents the creation of SnO2 nanoparticles, an alternative process of obtaining SnO2 electron transport materials, that can be achieved through a freeze-drying process of Tin(IV) precursors. Crystal growth of SnO2 can be controlled at significantly low temperatures at less than 40 o C.