Organic spacer engineering in 2D/3D hybrid perovskites for efficient and stable solar cells

Abstract

Perovskite solar cells (PSCs) have attracted widespread attention owing to their adjustable band gap, easy manufacturing, and longer carrier diffusion length. However, the influence of environmental factors such as water, oxygen, light and heat, as well as the inherent ionic characteristic of the perovskite crystal, make the stability of the device relatively poor. Here, organic cation ammonium salts, due to their hydrophobicity, are used as the 2D/3D hybrid perovskite isolation layer, and the spacer cation and inorganic [PbI₆]⁴⁻ octahedral structure could form multiple NH⋯I hydrogen bonds, which make the devices not only have the excellent long-term stability of 2D perovskites but also the high efficiency of 3D perovskites. At the same time, the EDS mapping results prove that ion migration and diffusion are significantly suppressed. As a result, in comparison with the control device (PCE = 19.41%), the PCE of the solar cell with a 2D capping layer based on PMAI is slightly increased to 20.02%, and the stability still maintains 93.02% of the original efficiency after 720 hours. In addition, both the long alkyl chain and the benzene ring can improve the hydrophobicity of the film, while the benzene ring can better enhance the humidity stability. This work provides a guide for developing 2D/3D PSCs to balance high efficiency and good long-term stability.