Improved Heterointerface Contact for Wide‐Bandgap and Tandem Perovskite Solar Cells

Abstract Perovskite‐based tandem solar cells represent a key technology for next‐generation photovoltaics. As an essential component, the carrier transport layer (CTL) encounters challenges such as poor interfacial contact and inefficient carrier transport in both single‐junction and tandem perovskite solar cells. Herein, it is demonstrated that inserting a 2,4,6‐Tris[3‐(diphenylphosphinyl)phenyl]‐1,3,5‐triazine (PO‐T2T) interlayer between C 60 and Atomic layer deposition (ALD) SnO X layers imparts multiple functional benefits: 1) The PO‐T2T interlayer re‐engineers the buried interface by establishing a more uniform surface potential and a favorable band alignment, thereby suppressing interfacial energetic disorder and enhancing electron‐extraction driving force, facilitating improved carrier transport; 2) The PO‐T2T interlayer provides nucleation sites for the uniform deposition of ALD SnO X and suppresses interfacial non‐radiative recombination, enabling improved heterointerface contact and enhanced device stability. As a result, high‐efficiency perovskite devices with enhanced operational stability are achieved: single‐junction wide‐bandgap (1.78 eV) perovskite cells with a power conversion efficiency (PCE) of 21.1%, and all‐perovskite tandem devices with PCEs of 28.5% (two‐terminal) and 29.3% (four‐terminal). This approach offers a promising strategy for advancing interfacial contact design in perovskite‐based tandem technology.