In Situ Interfacial Engineering in Perovskite Solar Cells: The Importance of Additives

Halide perovskite solar cells (PSCs) demonstrate exceptional power conversion efficiency and cost-effectiveness; however, their commercial viability is constrained by interfacial defects that compromise device performance and stability. While traditional interfacial modification techniques such as spin-coating perform effectively at laboratory scale, they present significant challenges when transitioning to large-area manufacturing processes. Recent research has focused on in situ interface engineering through the direct incorporation of molecular additives into perovskite precursor solutions. This strategy facilitates the in situ formation of beneficial interfacial architectures, including 2D/3D heterojunctions and passivation layers, thereby enhancing charge extraction efficiency while simultaneously reducing interfacial recombination losses. This review systematically analyzes the underlying mechanisms governing additive segregation at heterointerfaces and examines their multifunctional roles in (i) inducing dimensionally engineered phases, (ii) enhancing charge extraction through band alignment, and (iii) modulating nucleation kinetics to promote preferred crystallographic orientation. These precursor additive strategies represent promising pathways toward scalable manufacturing innovations that are essential for the successful commercialization of PSCs.