Enhancing Stability: Universal In-Situ Cross-Linking Strategy for Inverted Perovskite Solar Cells

Hole-selective self-assembled monolayers (SAMs) are thin organic films crucial in modern optoelectronic devices, especially in perovskite and silicon-perovskite tandem solar cells. However, their inherent instability often compromises device performance.

In a recent study published in Nature, a team led by Prof. Yang Chunlei and Assoc. Prof. Zhang Jie from the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, along with Prof. Alex K.-Y. Jen from City University of Hong Kong, introduced a universal in-situ cross-linking strategy to reinforce SAM molecules, addressing stability issues in high-efficiency inverted perovskite solar cells.

The team designed a novel azide-functionalized SAM molecule, JJ24, with an optimized carbon chain length. This molecule enhances the distribution uniformity of the host SAM molecule CbzNaph on a transparent conductive oxide (TCO) substrate while suppressing defects and voids during self-assembly.

The azide group in JJ24 can undergo thermal activation to form in-situ covalent cross-linking with alkyl chains of CbzNaph molecules, creating a tightly assembled co-SAM layer.

This structure improves the orientation of CbzNaph, reducing degradation at the perovskite buried interface and minimizing non-radiative recombination losses at the device interface.

By implementing this strategy, the researchers fabricated inverted perovskite solar cells with a certified power conversion efficiency (PCE) of 26.9%. These devices exhibited no efficiency degradation after 1,000 hours of continuous operation under ISOS-L-2 testing standards and retained over 98% of their initial PCE after 700 thermal cycles between –40°C and 85°C, demonstrating exceptional stability.

This study offers a practical approach to enhance the operational stability of high-efficiency SAM-based devices on rough substrates, with significant potential for advancing the commercialization of inverted perovskite photovoltaics and next-generation perovskite-based tandem solar cells.