Reversible Thermally Driven Phenyl Torsion in Self-Assembled Monolayers Releases Strain for Heat-Resilient Inverted...

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 cm²) and 24.24% (1 cm²).