Constructing robust heterointerfaces for carrier viaduct via interfacial molecular bridges enables efficient and stable inverted perovskite solar cells

A robust perovskite-substrate interface is critical to realize state-of-the-art inverted (p-i-n) perovskite solar cells (PSCs), as it enables charge carrier selectivity by means of suitable electrostatics, energy level alignment, and low interfacial recombination. To achieve this goal of carrier selectivity in p-i-n type PSCs, we propose a strategy of carrier viaduct via an interfacial molecular bridge comprised of Ph-CH2N+H3-n(CH3)(n) ammonium cations (where n is the degree of substitution). Through a joint theoretical-experimental study, we demonstrate that the most stable heterointerface is established by quaternary ammonium (QA, n = 3), where the -N+(CH3)(3) groups preferentially insert into the perovskite frameworks, with a vertical downward orientation of the phenyl groups towards the perovskite-substrates. This interfacial molecular bridge configuration as a carrier viaduct enables directional carrier management and redistributes a homogeneous environment at the heterointerface. Therefore, the carrier viaduct strategy enhances charge carrier extraction and transport in both in-plane or out-of-plane directions. Meanwhile, the bottom interfacial molecule acts as a double-sided molecular binder, maintaining the contact stack and strengthening the weak interface. The fabricated lab-scale inverted PSCs exhibit a champion efficiency of 25.45% (certified at 24.9%), with the fill factor exceeding 85.66%, corresponding to 95% of their thermodynamic limit at its bandgap (E-g = 1.54 eV). The corresponding perovskite solar modules for an active area of 23.25 cm(2) deliver an efficiency of 20.91%. Notably, even unencapsulated target PSCs retain nearly their initial efficiency after 3000 hours under light soaking at maximum power point tracking.