Engineering Pyreno[1,2-b:8,7-b′]dithiophene-Based Conjugated Polymers for Efficient and Stable Perovskite Solar Cells

The advancement of p-type conjugated polymers with optimized electrical properties, morphology, and heat tolerance is essential for n-i-p-type perovskite solar cells. Herein, we present a novel conjugated polymer, p-PDT₁₄4-E, composed of alternating units of 4,4,7,7-tetrakis(4-hexylphenyl)-4,7-dihydropyreno[1,2-b:8,7-b′]dithiophene (PDT₁₄4) and 3,4-ethylenedioxythiophene. This copolymer was synthesized via a palladium-catalyzed direct arylation polycondensation method. Compared to the corresponding homopolymer p-PDT₁₄4 synthesized by oxidative polymerization, p-PDT₁₄4-E exhibited an elevated highest occupied molecular orbital energy level, facilitating faster hole extraction and enhanced hole conductivity. Additionally, p-PDT₁₄4-E demonstrated an increased glass temperature and a more uniform film morphology. When used as a hole transport material along with the air doping promoter 4-(tert-butyl)pyridinium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide, perovskite solar cells incorporating p-PDT₁₄4-E achieved an average power conversion efficiency (PCE) of 25.5%, surpassing reference cells using spiro-OMeTAD (average PCE of 24.7%) under identical conditions. Furthermore, p-PDT₁₄4-E-based cells exhibited excellent operational stability at 45 °C and thermal storage stability at 85 °C.