A faster chemical bath deposition method for SnO2 ETLs in perovskite solar cells

• Main Author: Wong, Zi Sheng
• Other Authors: Nripan Mathews
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/156302
• Institution: Nanyang Technological University

Perovskite Solar Cells (PSC) has been a topic of interest in recent times. Key advantages such as low costs, lightweight, and ability to react to different wavelengths of sunlight, make PSC an attractive counterpart to standard silicon solar cells. Being in development for far less time than silicon solar cells, efficiencies have already been reported to reach above 20 percent, showing further promise in the material. [1] This project aims to provide a comprehensive study on improving reproducibility of PSCs by investigating means to layer the electron transporting layer in the form of tin oxide, in a compact and uniform manner. The devices synthesized were tested using two methods, solar simulation, and cyclic voltammetry. Furthermore, device characterisations such as Scanning Electron Microscopy, Ultraviolet-visible spectroscopy and photoluminescence were done. Initial studies on the effect of pre-mixing sonication indicated positive device results, especially for a duration of 40 minutes. The experiment shows that there exists an optimal mixing time, and that pre-mixing stage is essential to the outcome of the devices. The next study examines the practicality of utilising sonication to yield a faster CBD reaction, as well as better ETL blocking capacity. Results from the experiment indicated the merits in sonication. Devices that underwent an extended duration of sonicated CBD displayed more optimal blocking layers. Another study attempts to increase SnO2 concentration by two times original amount, to improve coverage. The experiment yielded good J-V data, whilst noting poor device reproducibility. Finally, the last study aims to further increase SnO¬2 concentration to three times original amount. The experiment yielded better J-V data when compared to two times concentration, however it was noted that coverage was not as good. Hence, the experiment suggests that the best possible coverage may not necessarily go hand in hand with improving device data. Overall, results obtained gave a better understanding in ways to speed up CBD and improve coverage as well as yield. It is hence useful for future applications such as commercialisation. However, more studies are still required to find out the chemical reaction mechanisms and growth mechanisms to further improve yield.