Damage-Free Process of Metal Electrode Using Plasma-Assisted Vapor Deposition for Halide Perovskite Devices

In response to fossil fuel depletion and global warming, research and development of new and renewable energy are recognized as crucial tasks worldwide. Solar cells, which utilize unlimited solar energy to generate electricity in an environmentally friendly manner, are at the forefront of new renewable energy technologies. Next-generation perovskite solar cells have emerged as promising candidates, owing to their cost-effectiveness and simplified low-temperature processes. The structure of a perovskite solar cell typically consists of glass/transparent electrode/electron transport layer/perovskite (light absorption layer)/hole transport layer (HTL)/metal electrode. The HTL, predominantly composed of organic materials like Spiro-OMeTAD, PTAA, and P3HT, etc. is susceptible to plasma damage when metal electrodes are formed using the commonly employed vacuum physical vapor deposition (PVD) method, limiting its utility. Although the thermal evaporation method is employed in the metallization process, it also carries the disadvantage of uneven metal particle deposition, resulting in reduced transparency and conductivity of the thin film. To overcome these challenges, this research focuses on fabricating perovskite solar cells with high-quality and damage-free metal electrode deposition on organic materials using plasma-assisted vapor deposition (PAVD). Unlike conventional methods, PAVD technology does not require heating the substrate to enhance the thin film. Instead, it converts the interior of the thermal evaporation source into a plasma state, thereby transforming the metal particles into a high-energy state. As a result, the metal particles firmly bond to the substrate without the need for additional energy, like heat. This process results in the formation of high-quality and low-resistance metal thin films. The morphology, structure, and electrical characteristics of the metal thin film formed using PAVD were compared with those obtained using the thermal evaporation method. Furthermore, the relationship between the deposition method and the device characteristics was investigated. Given the critical importance of metal electrode quality and resistance in large-area perovskite monolithic modules, this research also concentrated on their application in large-area modules. The large-area perovskite modules fabricated with the PAVD metal electrode show over a 1% improvement in efficiency compared to those using the evaporation method. In addition, improvements in long-term stability characteristics were observed. In the future, the PAVD technology is expected to be highly utilized as a damage-free electrode deposition process for electronic devices using organic thin film layers due to its high quality and low resistance.