Abstract
Over the past decade perovskite solar cells (PSCs) have quickly established themselves as a
promising technology boasting both high efficiency and low processing costs. The rapid
development and success of PSCs is a product of substantial research effort addressing
compositional engineering, thin film fabrication, surface passivation and interfacial
treatments. Recently, engineering of the device architecture has entered a renaissance with the
emergence of several new bulk and graded heterojunction structures. These structures
promote a lateral approach to the development of single-junction PSCs affording new
opportunities in light management, defect passivation, carrier extraction and long-term
stability. Following a short overview of the historic evolution of PSC architectures, we offer a
detailed discussion of the promising progress of the recently reported perovskite bulk
heterojunction (BHJ) and graded heterojunction (GHJ) approaches. To enable better
understanding of these novel architectures, a range of approaches to characterizing the 2
architectures are presented. Finally, an outlook and perspective are provided offering insights
into the future development of PSC architecture engineering.