Grain-boundary grooves in perovskite solar cells

As a general materials phenomenon driven by thermodynamics, grain boundary network, when extending onto the film surface or interface, can create an intriguing grooving geometry. Such formed grain-boundary grooves (GBGs) invariably influence the heterointerface microstructures in perovskite solar cells (PSCs). Herein, we present a unique, focused discussion on this prominent yet rarely studied microstructure type. In this perspective, we first illustrate the fundamental theories that govern the formation of GBGs and their dynamics. Then, we envision the effects of GBGs on carrier transport, chemical stability, and mechanical reliability of perovskite thin films. Finally, we propose possible engineering methods to tailor GBGs for PSCs with enhanced efficiency and durability.