Supramolecular Stabilization of Wide-Bandgap Perovskites Enables Durable Perovskite-Organic Tandem Solar Cells.

Abstract

Perovskite-organic tandem solar cells (PO-TSCs) offer a compelling platform for flexible photovoltaics by combining wide-bandgap (WBG) perovskite top cells with mechanically compliant organic rear cells. However, their long-term stability is critically limited by the intrinsic instability of WBG mixed-halide perovskites. Here, through systematic ageing and mechanistic analyses, we identify halide phase segregation in the WBG perovskite sub-cell under photothermal stress as the dominant degradation pathway that dictates the operational stability of the PO-TSC investigated here. To address this challenge, we develop a halogenated cyclodextrin-based supramolecular strategy that enables precise regulation of perovskite crystallization, defect passivation and halide distribution. Synergistic host-guest, hydrogen-bonding, halogen-bonding and coordination interactions simultaneously regulate crystallization and suppress ion migration to result in stabilized halide homogeneity. Consequently, 1.80-eV WBG devices achieve 20.60% efficiency with improved operational stability. Integrated PO-TSCs deliver an efficiency of 27.17% (certified 26.3%) together with T80 lifetimes of 1100 h under maximum power point tracking (MPPT) operation and T85 lifetimes of 1128 h under thermal stress of 85°C, while flexible PO-TSCs reach an efficiency of 24.00%. This work defines a general supramolecular design paradigm for efficient, durable and flexible tandem photovoltaics.