Beyond two-dimension: One- and zero-dimensional halide perovskites as new-generation passivators for high-performance perovskite solar cells

Perovskite solar cells (PSCs) as a rising star in the photovoltaic field have received rapidly increasing attention recently due to the boosting power conversion efficiencies (PCEs) from 3.8% to 25.7% in the last 13 years. Nevertheless, the conventional PSCs with three-dimensional (3D) halide perovskites as light absorbers suffer from inferior PCEs and poor durability under sunlight, high-temperature and humid conditions due to the high defect amount and structural instability of 3D perovskites, respectively. To tackle these crucial issues, lower-dimensional halide perovskites including zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) perovskites have been employed as efficient passivators to boost the PCEs and durability of 3D-PSCs due to the high structural stability and superior resistance against moisture, heat and sunlight. Therefore, in order to achieve better understanding about the advantages and superiorities of combining low-dimensional perovskites with their 3D counterparts in improving the PCEs and durability of 3D-PSCs, the recent advances in the development and fabrication of mixed-dimensional PSCs with 1D/0D perovskites as passivators are summarized and discussed in the review. The superiority of 1D/0D perovskites as passivators over 2D counterparts, the passivation mechanism and the methods of 1D/0D perovskites are also presented and discussed. Furthermore, the rules to choose 1D/0D perovskites or relevant spacer cations are also emphasized. On this basis, several specific strategies to design and fabricate mixed-dimensional PSCs with 1D/0D perovskites are presented and discussed. Finally, the crucial challenges and future research directions of mixed-dimensional PSCs with 1D/0D perovskites as passivators are also proposed and discussed. This review will provide some useful insights for the future development of high-efficiency and durable mixed-dimensional PSCs.