Strategies for performance and stability advancement in multicomponent perovskite photovoltaics

Abstract

The unique photophysical properties of halide perovskites have placed them ahead of other photovoltaic (PV) materials in the areas of photoconversion efficiency (PCE) and energy level alignment with common contacts. The PCE is currently closing in on the predicted theoretical limit. However, the poor stability of this class of materials under ambient conditions is a drawback. It has limited the extensive exploitation of their properties and has slowed down their uptake in the global PV market. Notably, the unique properties have been attributed to the optimal orbital overlap between the lead cation (Pb²⁺) and halide anion making up the inorganic framework of the crystal lattice. Although Pb is toxic, its presence is key to the unique opto-electronic properties of halide perovskites. Therefore, it must be retained while measures are taken to stabilize the lattice so as to suppress Pb leakage and the migration of other ionic components. One way to approach this is by multiple lattice site substitution which yields a multi-component perovskite (ABX₃) configuration, where the A-, B- and X-sites are occupied by more than one element which can synergistically compensate for the composition-induced instability through an increase in ion migration activation energy. The resulting multi-component perovskite (MCP) is commonly known as multi-cation mixed-halide perovskite. Therefore, in this review, we discuss the various approaches adopted recently to achieve higher stability in MCPs. The approaches are grouped into the focus areas of material identification, composition engineering, materials engineering, defect passivation, phase stabilization, photophysical property enhancement and device engineering. We discuss the challenges in stability evaluation of perovskite PV devices. Finally, we draw conclusions based on the various reports and give an outlook on pertinent research directions to further advance the PV applications of MCPs.