Vacuum Deposition Engineering toward Highly Efficient, Stable, and Scalable Perovskite Solar Cells

Abstract

Humanity has made great efforts to secure energy since industrialization, and recently, due to the crisis of climate change, the development of low-carbon technology for realizing carbon neutrality and green growth has emerged as a major concern worldwide, as well as the interest of developing sustainable renewable energy sources is also getting a lot of attention. Among various types of renewable energy, solar cells that convert nearly infinite solar energy into electricity have been developed and manufactured due to their various advantages. Recently, perovskite solar cells have received great attention as the next-generation solar cells, and the record power conversion efficiency have reached more than 25% in a short period of time. Amid this positive research trend, interest in the commercialization of perovskite solar cells is increasing, but most of the currently reported researches are based on solution methods, such as spin coating, which is easy to manufacture in a laboratory scale but limited as a mass production process. On the other hand, the vacuum deposition method is a technology commonly used in the thin film and semiconductor industries for large-scale and mass production. Considering future productivity and overall cost, there is no doubt that vacuum deposition-based perovskite solar cell technology will be a key breakthrough in the commercialization of perovskite solar cells-based on its excellent potential. The purpose of this thesis is to develop a vacuum deposition method for the fabrication of perovskite films and integrate them into solar cells using various charge transport layers. Besides development of vacuum deposition of perovskite, interface engineering is considered as a valid strategy to improve perovskite solar cell performance. Therefore, the influence of different charge transport layer and interfacial materials on the performance of perovskite solar cells is also studied in this thesis. In addition, in this thesis, the author was demonstrated on large-area, tandem solar cells based on vacuum-deposited perovskite to develop large-area, high-efficiency technology that is important for the commercialization of next-generation solar cells. The thesis is consisted of the following chapters: In Chapter 1, the background, general information, characteristics, and analysis methods of solar cells were introduced. Among them, the characteristics and trends of vacuum deposition-based perovskite suitable for next-generation solar cells were discussed. In Chapter 2, various strategies for fabricating high-efficiency perovskite solar cells based on vacuum deposition were introduced. The basic vacuum deposition process method, vacuum deposition process optimization, and perovskite thin film characteristics were discussed. In addition, the introduction of post annealing treatment and post solvent treatment was discussed to improve the quality of perovskite film and solar cells. Finally, the optimization of perovskite composition was described toward the fabrication of high-efficiency, high-stability perovskite solar cells. In Chapter 3, the vacuum deposited perovskite passivation layer was discussed. We adjusted the orientation of the perovskite passivation layer by controlling the parameters of the vacuum deposition process. Through this, we reported research results that improved the stability of the vacuum-deposited perovskite solar cell and at the same time improved the charge transport performance and solar cell efficiency. In Chapter 4 and 5, we discussed on the vacuum deposition-based hole transport layer, especially Spiro-OMeTAD and PTAA derivative. Spiro-mF, discussed in this thesis, has superior charge transport properties compared to the existing Spiro-OMeTAD, and the excellent perovskite solar cell stability and efficiency are improved according to the characteristics of being formed by vacuum deposition. In addition, TAA-tetramer with low energy disorder was applied as HTL to show the possibility of next-generation HTL. In Chapter 6, the large-area perovskite solar cell and module based on vacuum deposition was discussed. By the deposition technologies discussed in the previous chapter, a large-area single solar cell and solar module was demonstrated based all vacuum deposition, including the perovskite layer, charge transport layer, and electrode. It was confirmed that the efficiency loss according to the increasing area was suppressed in vacuum processed perovskite solar cell compared to the solution processed perovskite solar cell. In Chapter 7, we discussed tandem solar cells based on vacuum-deposited perovskite as top cell on the silicon bottom cell. And the vacuum deposited film conformability was investigated on textured silicon surface.