Simple adjustments to the molecular planarity of organic sensitizers: towards highly selective optimization of energy levels

Abstract

As a key property, the energy levels of organic sensitizers generally cannot be adjusted with good selectivity and high efficiency. Thus, a new regulation strategy is urgently needed. Herein, by simply replacing phenyl by a thienyl unit in a π-bridge segment, two novel quinoxaline sensitizers, CS-9 and CS-10, based on D–A–π–A construction have been designed and synthesized. With this simple modification, the planarity of the auxiliary acceptor-to-acceptor part is effectively improved. Along with this specified planarization of the molecule, the LUMO levels of the dyes are selectively stabilized. Our results demonstrate that the planarity adjustment to a specified molecular structure is obviously preferred to selectively optimize the energy levels and photovoltaic performances of the sensitizer, providing a powerful strategy for the development of highly efficient organic sensitizers in the future.