Triphenylamine-ethylenedioxythiophene copolymers for perovskite solar cells: impact of substituent type and alternation

Abstract

Developing cost-efficient p-type polymeric semiconductors with superior quality factors, such as energy levels, hole transport, and mechanical properties, is crucial for enhancing the performance of n-i-p perovskite solar cells. In this study, we synthesized three triphenylamine-ethylenedioxythiophene alternating copolymers via direct arylation polycondensation. The first polymer features three methyl groups on the non-main chain phenyl rings, the second has one 2-octyldodecyloxy group, and the third incorporates a combination of half three methyl groups and half one 2-octyldodecyloxy group. Variations and combinations of these substituents resulted in differences in molecular weights, glass transition temperatures, highest occupied molecular orbital energy levels, and film morphologies. Compared to reference polymers with only one type of substituent, the synergistic use of different substituents led to polymeric semiconductor composite films with smoother morphology and higher conductivity. Utilizing this uniquely substituted p-type polymeric semiconductor, we fabricated perovskite solar cells with an average power conversion efficiency of 25.4%. These cells exhibited excellent stability under thermal storage at 85 oC and operational conditions at 45 oC.