Black phosphorus is a new type of two-dimensional semiconductor material that has attracted extensive attention because of its tunable direct band gap and high carrier mobility. Compared with bulk black phosphorus, low-dimensional black phosphorus has a greater potential application value because of its structural and performance advantages. In recent years, many research groups have successfully prepared low-dimensional black phosphorus with different morphologies and applied them to the active layer, electron transport layer, and hole transport layer of solar cells, such that the conversion efficiency is improved to different degrees. This study introduces a preparation method of low-dimensional black phosphorus, focuses on its research progress in the field of solar cells, puts forward the problems that must be solved, and forecasts the future development trend of low-dimensional black phosphorus.