Interface engineering for highly efficient and stable perovskite solar cells and their applications

Abstract

Interface engineering is crucial for achieving highly efficient and stable perovskite solar cells (PSCs). Here, we present a unified strategy that employs organic passivation layers at interfaces in both n–i–p and p–i–n device configurations. In the n–i–p configurations, a newly synthesized bathocuproine-based polyelectrolyte (poly-BCP) was introduced between the SnO₂ electron transport layer (ETL) and the perovskite absorber. This interlayer effectively passivated oxygen-vacancy defects at the SnO₂ side while simultaneously scavenging ionic defects at the perovskite side, thereby suppressing both bulk and interfacial nonradiative recombination. As a result, the modified PSCs achieved a power conversion efficiency (PCE) of 24.4% with an open-circuit voltage of 1.21 V, and retained 93% of their initial efficiency after 700 hours of continuous one-sun irradiation under inert conditions without encapsulation. For the p–i–n configuration, amine-functionalized organic small molecules (e.g., PBN) were employed as passivation layers at the interface between the PCBM electron transport layer and the copper electrode. Strong Cu–N coordination facilitated the dense growth of Cu electrodes with strong adhesion, effectively blocking moisture ingress. Consequently, non-encapsulated devices retained 90% of their initial PCE after 200 days under ambient air (25 °C, 20–40% relative humidity), and showed negligible degradation even under harsher conditions such as high humidity or direct water immersion. Furthermore, we extended this approach to quasi-two-dimensional Ruddlesden–Popper perovskites (RPPs), which are inherently more stable but typically less efficient than their 3D counterparts. By applying a multifunctional organic molecule as a surface passivation treatment on RPP films (PEA₂MA₄Pb₅I₁₆, ⟨n⟩ = 5) in p–i–n devices, both surface and deep-level traps were effectively suppressed through electrostatic interactions, while preferred out-of-plane crystal orientation was induced. These effects facilitated efficient carrier transport, leading to a PCE of 20.05% with negligible hysteresis. The optimized devices maintained 88% of their initial efficiency after 1000 hours of continuous one-sun operation under maximum power point tracking, without encapsulation or UV filtering.