Abstract: Since the preparation of the first perovskite solar cell device, the photoelectric conversion efficiency of perovskite solar cells has jumped from 3.8% to 26.1%, making them a favorable competitor for the next generation of commercial solar cells. In the past decade, tin oxide has become the preferred electron transport layer material for n-i-p perovskite solar cells due to its suitable band structure, good electron transfer performance, simple preparation process, and good chemical stability. Although tin oxide electron transport layer has many advantages, there are still issues that need to be improved in terms of electron transport performance, such as energy level shift between the transport layer and the perovskite layer, interface defects causing significant loss of photo generated carriers, and poor film-forming performance that is prone to pinholes. In view of this, this article summarizes the main reasons for the formation of the above problems, and analyzes the research results of different solution doping processes such as metal ion doping, halogen ion doping, organic molecule doping, and nanoparticle doping. It elucidates the advantages and disadvantages of different doping processes in solving the defects of solution based tin oxide thin films and their applications in perovskite battery devices, and makes prospects for optimizing the performance of doped tin oxide transport layers in perovskite devices.