In long-term outdoor operation, both crystalline silicon solar cells and thin film solar cells are subject to potential-induced degradation (PID), decreasing the output power of photovoltaic modules. Despite numerous studies in the past, the understanding of the PID phenomenon and its solutions is still incomplete. In order to promote a deeper understanding of the PID phenomenon in solar cells and provide guidance for stability research of solar cells, the causes of PID in crystalline silicon solar cells and thin film solar cells, as well as related solutions are reviewed in this paper.