An alternating copolymer of phenothiazine and ethylenedioxythiophene for perovskite solar cells: effects of flexible and rigid substituent alternation.

Developing p-type polymeric semiconductors with exceptional electrical performance, heat tolerance, and cost-effectiveness is pivotal for advancing the practical application of n-i-p perovskite solar cells. Here, we employed direct arylation polycondensation to synthesize an alternating copolymer of phenothiazine and 3,4-ethylenedioxythiophene, featuring a high glass transition temperature (175 °C). In addition to the alternation of conjugated units within the main chain, the copolymer features alternating flexible (2-octyldodecyl) and rigid (trimethylphenyl) substituents at the nitrogen positions of the phenothiazine moiety. Compared to reference polymers with solely flexible or rigid substituents, the alternating use of these moieties resulted in the polymeric semiconductor composite film with smoother morphology and enhanced hole mobility. By employing this polymer with a distinct distribution of substituents and an innovative main chain structure as a hole transport material, we fabricated perovskite solar cells achieving an average efficiency of 25.1%. These cells also exhibited excellent stabilities under conditions of 85 °C thermal storage and 45 °C operation.