This paper systematically examines the role of large-scale language models (LLMs) in UI/UX design by analyzing 38 peer-reviewed papers published from 2022 to 2025. We identify use cases of major LLMs, including GPT-4, Gemini, and PaLM, and analyze how they are integrated across the entire design process from ideation to evaluation. We present general methodologies, including prompt engineering, human-machine collaborative workflows, and multimodal input, and show that while LLMs transform the design process, they still face persistent challenges, such as hallucinations, prompt instability, and limits to explainability. In conclusion, we present LLMs as new collaborators in the design field and suggest ethical, inclusive, and effective ways to integrate these technologies.