Aza[5]helicene‐Derived Semiconducting Polymers for Improved Performance in Perovskite Solar Cells: Exploring Energetic and Morphological Influences

The strategic design of solution‐processable semiconducting polymers possessing both matched energy levels and elevated glass transition temperatures is of urgent importance in the progression of thermally robust n‐i‐p perovskite solar cells with efficiencies exceeding 25%. In this work, we employed direct arylation polymerization to achieve the high‐yield synthesis of three aza[5]helicene‐derived copolymers with distinct HOMO energy levels and exceptional glass transition temperatures. Upon integration of these semiconducting polymers into formamidinium lead triiodide‐based perovskite solar cells, marked disparities in photovoltaic parameters manifest, primarily stemming from variations in the electrical conductivity and film morphology of the hole transport layers. The p‐A5HP‐E‐POZOD‐E copolymer, featuring a conjugated main chain comprising alternating repeats of aza[5]helicene, ethylenedioxythiophene, phenoxazine, and ethylenedioxythiophene, attains an initial average efficiency of 25.5%, markedly surpassing reference materials such as spiro‐OMeTAD (23.0%), PTAA (17.0%), and P3HT (11.6%). Notably, p‐A5HP‐E‐POZOD‐E exhibits a high cohesive energy density, resulting in enhanced Young's modulus and diminished external species diffusion coefficients, thereby conferring perovskite solar cells with exceptional 85°C tolerance and operational stability.