A Phenoxazine-Based Alternating Copolymer for Efficient and Durable Perovskite Solar Cells

Developing cost-effective p-type semiconducting polymers with desirable electrical properties and thermal tolerance is essential for the practical application of n-i-p type perovskite solar cells. In this study, we synthesized a semiconducting copolymer, p-POZOD-ENEM, via direct arylation polycondensation. This copolymer features an alternating main chain of phenoxazine, ethylenedioxythiophene, dimethoxynaphthalene, and ethylenedioxythiophene. The theoretical HOMO energy level of p-POZOD-ENEM is 70 meV deeper than that of the homopolymer poly(10-(2-octyldodecyl)phenoxazine-3,7-diyl) (p-POZOD), yet both are comparable to the established material spiro-OMeTAD. Furthermore, p-POZOD-ENEM exhibits higher glass transition temperature, hole mobility, and conductivity than both p-POZOD and spiro-OMeTAD, along with enhanced film morphology. Perovskite solar cells utilizing p-POZOD-ENEM as the hole transport material achieved an average power conversion efficiency of 25.0% and maintained good stability under thermal storage at 85 °C and operation at 45 °C.