Reversible Thermally Driven Phenyl Torsion in Self‐Assembled Monolayers Releases Strain for Heat‐Resilient Inverted Perovskite Solar Cells

Abstract

Abstract Perovskite solar cells (PSCs) long‐term stability remains constrained by intrinsic strain induced by thermal processes and fluctuating operating conditions. Here, we introduce a carbazole‐based self‐assembled monolayer (SAM) hole transporting layer, (6‐(3,6‐diphenyl‐9H‐carbazol‐9‐yl)hexyl) phosphonic acid, termed as Torsioner SAM, which features reversible, thermally driven phenyl torsion behavior. Spectroscopic and theoretical investigations confirm a dynamic, linear modulation of the torsion angle by 0.07° K −1 within the critical temperature window spanning perovskite deposition and practical operation. The Torsioner SAM with two thermal driven phenyl units serves as a molecular buffer, effectively releasing residual strain caused by interfacial mismatch. Furthermore, the Torsioner SAM mitigates thermal activated lattice distortions and continuously dissipates additional strain under operational temperature variations. As a result, the corresponding devices exhibit markedly improved isothermal and thermocycling stabilities, retaining over 91.3% of their initial efficiency after 1000 h under the ISOS‐D‐2I protocol and 94.4% after over 200 thermal cycles (25–85 °C) under the ISOS‐T‐1 protocol. The incorporation of the Torsioner SAM also suppresses non‐radiative recombination and enhances hole transport, yielding champion power conversion efficiencies of 26.26% (0.09 cm 2 ) and 24.24% (1 cm 2 ).