Impacts of linking units of porphyrin dimer donors on the performance of organic solar cells†

Abstract

Dimer photovoltaic materials have emerged as one of the most promising types of organic solar cell (OSC) materials due to their well-defined chemical structures and long-term device stability. However, current research on dimeric photovoltaic materials primarily focuses on acceptors, while the studies on dimer donors have been relatively limited. In this study, we designed and synthesized three porphyrin dimer donors E-ZnP₂, BT-ZnP₂ and BDT-ZnP₂ by linking two functionalized D–A (D: electron donor unit and A: electron acceptor unit) porphyrins with ethynylene, diethynylene-benzothiadiazole (BT) and diethynylene-benzodithiophene (BDT), respectively. The impacts of the linking units on their energy levels, absorption properties, aggregation behaviors and photovoltaic performance are investigated. Among the three devices with porphyrins as the electron donors and Y6 as the electron acceptor, the E-ZnP₂-based cells exhibit superior charge mobility and reduced charge recombination due to the stronger molecular aggregation of E-ZnP₂ and the improved miscibility with Y6, resulting in an impressive power conversion efficiency (PCE) of 9.64%. The findings offer valuable guidelines for developing dimer donor materials.