No abstract

Perovskite solar cells (PSCs) have recently demonstrated high efficiencies of over 22%, but the thermal stability is still a major challenge for commercialization. In this work, the thermal degradation process of the inverted structured PSCs induced by the silver electrode is thoroughly investigated. Elemental depth profiles indicate that iodide and methylammonium ions diffuse through the electron‐trasnporting layer and accumulate at the Ag inner surface. The driving force of forming AgI then facilitates the ions extraction. Variations on the morphology and current mapping of the MAPbI3 thin films upon thermal treatment reveal that the loss of ions occurs at the grain boundaries and leads to the reconstruction of grain domains. Consequently, the deteriorated MAPbI3 thin film, the poor electron extraction, and the generation of AgI barrier result in the degradation of efficiencies. These direct evidences provide in‐depth understanding of the effect of thermal stress on the devices, offering both experimental support and theoretical guidance for the improvement on the thermal stability of the inverted PSCs.

The perovskite solar cell has emerged rapidly in the field of photovoltaics as it combines the merits of low cost, high efficiency, and excellent mechanical flexibility for versatile applications. However, there are significant concerns regarding its operational stability and mechanical robustness. Most of the previously reported approaches to address these concerns entail separate engineering of perovskite and charge-transporting layers. Herein we present a holistic design of perovskite and charge-transporting layers by synthesizing an interpenetrating perovskite/electron-transporting-layer interface. This interface is reaction-formed between a tin dioxide layer containing excess organic halide and a perovskite layer containing excess lead halide. Perovskite solar cells with such interfaces deliver efficiencies up to 22.2% and 20.1% for rigid and flexible versions, respectively. Long-term (1000 h) operational stability is demonstrated and the flexible devices show high endurance against mechanical-bending (2500 cycles) fatigue. Mechanistic insights into the relationship between the interpenetrating interface structure and performance enhancement are provided based on comprehensive, advanced, microscopic characterizations. This study highlights interface integrity as an important factor for designing efficient, operationally-stable, and mechanically-robust solar cells.