Soo, Jing Yuan (2023) Synthesis of cadmium selenide and cadmium telluride co-sensitised quantum dots via the silar method. Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

Third generation solar cells such as Quantum Dot Sensitized Solar Cell (QDSSC) have the potential to overcome the Shockley-Queisser limit and achieve higher efficiency than the first and second generations. However, there are still challenges in achieving the theoretical efficiency for QDSSC, which is still an open space for further research. Among the various materials used for QDSSC, CdSe quantum dots (QDs) are widely used as it can be tuned to absorb a wide range of absorption wavelength. However, there are still limitation in the absorption wavelength up to near infra-red region that can be further improved with method such as co-sensitizing with another material such as CdTe. In this study, successive ionic layer adsorption and reaction (SILAR) method was used to co-sensitized CdSe/CdTe QDs with onto titanium dioxide (TiO2) nanorods array grown on Fluorine doped Tin Oxide (FTO) coated glass. Three variation of SILAR method were used to synthesize CdSe QDs on TiO2 nanorods with 1-8 number of cycles. This first step was used to understand the effect of SILAR method on CdSe QDs and to select the best SILAR method to proceed with the synthesis of CdTe QDs. The CdSe QDs with best absorption result were then used to be co-sensitized with CdTe QDs. Among the three variation of SILAR methods, the inverse SILAR method shown the highest consistency in absorption intensity using the UV-Vis spectroscopy. The increase in the number of SILAR cycles resulted in the increase in the amount of QDs and the aggregation was clearly observed around seven cycles onwards as observed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). It was found that five cycles were the optimum cycle to avoid the aggregation and yet achieve the highest absorption intensity. Hence, CdSe(5) sample were chosen to be further co-sensitized with CdTe QDs. The co-sensitized sample, CdSe(5)CdTe(5), shows a higher absorption intensity and wider absorption range as compared to the CdSe(5) sample. Furthermore, the CdSe(5)CdTe(5) sample shows the highest efficiency of 0.018 % measured using the electrochemical impedance spectroscopy (EIS) and solar simulator. This conclude that the co-sensitization was able to improve in harvesting ability

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