2D and quasi-2D hybrid perovskites containing organic cations with an extended conjugated system: opportunities and challenges

Abstract

2D and quasi-2D hybrid perovskites have been in the spotlight for the past few years due to their generally enhanced environmental stability compared to their 3D counterparts and a much higher degree of compositional and structural flexibility. Incorporating organic cations with an extended conjugated system presents a sub-field of research that is gaining increasing attention due to the potential of creating hybrids with new and improved material properties. This includes the emergence of charge- and energy-transfer processes between the organic and inorganic layers, enhanced charge carrier transport, reduced exciton binding energy, and superior stability. However, incorporating organic cations with an extended conjugated system generates additional challenges. The processing of thin films as well as the growth of single crystals needs to be optimised. Control over the crystal structure obtained from the precursor components under the conditions for thin film deposition and crystal growth needs to be achieved. The rational design of the molecular structure of the organic cation in combination with a specific inorganic framework to achieve the desired properties presents the final challenge. In this perspective, we provide a critical analysis of the opportunities and challenges associated with the use of conjugated organic cations in 2D and quasi-2D hybrid perovskites.