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

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 C₆₀ 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.