Emerging trends in interface processing: a comparative review of conventional and inverted perovskite solar cells

Abstract Perovskite solar cells have gained significant attention due to their rapid efficiency improvements and low-cost manufacturing potential. With power conversion efficiencies exceeding 25% in recent years, PSCs are now considered strong contenders in the photovoltaic research area. The perovskite structure, typically represented as ABX₃, provides exceptional optoelectronic properties such as broad light absorption, tunable bandgaps, long carrier diffusion lengths, and low exciton binding energies. These advantages enable solution-based fabrication methods compatible with large-scale production and flexible substrates. PSCs are mainly classified into conventional (n–i–p) and inverted (p–i–n) architectures, based on the order of the electron and hole transport layers. While both structures operate on similar principles, the interfaces between the perovskite absorber and transport layers play a key role in charge extraction, device stability, and crystallization. Common transport materials like SnO2, PTAA, and PEDOT:PSS face challenges related to high cost, poor stability, and detrimental chemical interactions. Besides that, the use of dopants such as LiTFSI and TBP can improve conductivity but often reduce long-term stability. As a result, research is focused on developing new interface materials that combine high mobility, stability, low cost, and good energy alignment. This review highlights recent advancements in interface engineering to enhance both efficiency and durability in PSCs.