Two-dimensional （2D） perovskite materials have been receiving considerable attention owing to their high stability. Despite this，there is still significant potential for improving their power conversion efficiency. Designing effective spacer cations is one of the crucial methods to improve the photoelectric performance of 2D perovskite solar cells. Among the various strategies，halogen substitution has emerged as a particularly effective approach，which can fine-tune the stability and optical properties of the perovskite crystal structure，leading to notable improvements in photoelectric conversion efficiency as well as long-term stability. In recent years，there has been significant and notable progress of two-dimensional （2D） perovskites based on various halogen-substituted spacer cations in the preparation of high-performance perovskite solar cells. This paper initially provides a comprehensive overview of the development status of 2D perovskite materials and devices that employ different spacer cations. Following this，the focus shifts to an in-depth review of the advancements made in the fabrication of 2D perovskite solar cells （PSCs） and the surface modification of three-dimensional （3D） perovskites，specifically emphasizing the role of spacer cations that have been singly or multiply substituted with halogens such as fluorine，chlorine，and bromine. Finally，we present a concise discussion on the current challenges faced in this field and offer insights into the potential future directions for further research and development.

Contents

1 Introduction

2 2D perovskite materials and devices with different spacer cations

3 Characteristics of halogen-substituted spacer cation-based 2D perovskites and their applications in photovoltaic devices

3.1 Research on halogen-substituted spacer cation-based 2D perovskites and photovoltaic devices

3.2 Research on halogen-substituted 2D perovskite surface modification of 3D perovskites

4 Conclusion and future perspectives on halogen-substituted 2D perovskites