A Helicene-Based Molecular Semiconductor Enables 85 °C Stable Perovskite Solar Cells

The poor tolerance of ionic perovskite light-absorption layers to water vapor, thermal stress, and bias potential poses remarkable challenges for the selection of other essential elements of solar cells, which should be capable of inhibiting the degradation of perovskite while maintaining their own electronic functions, in particular, under the long-term thermal stress at 85 °C. We herein report a molecular semiconductor of bis(9-methyl-9H-carbazol-3-yl)amine-functionalized thia[5]helicene, which not only presents a glass temperature (Τg) of 248 °C but also has a kinetic solubility of more than 350 mg mL–1 in a green solvent. Its doped composite with a conductivity of 27.5 μS cm–1 still holds a Τg of 177 °C, enabling the fabrication of 21% efficiency, 85 °C stable perovskite solar cells for 1000 h. The cells also display an operation stability under continuous full sunlight at 60 °C.