Impact of LUMO Energy Level on n-Type Doping Efficiency and Air Stability of Conjugated Polymers

While p-type doping of conjugated polymers has been extensively studied, the development of efficient and stable n-type doping remains a significant challenge. Although the importance of the LUMO (lowest unoccupied molecular orbital) energy level of conjugated polymers on effective n-type doping has been widely recognized, there are few systematic studies to quantify the influence of the LUMO level on n-type doping of conjugated polymers. In this work, we synthesized a series of BDOPV-based conjugated polymers with tunable LUMO energy levels (− 4.05 to −4.37 eV) by incorporating fluorine atoms and cyano (−CN) groups onto an otherwise identical conjugated backbone. Our results revealed that a deeper LUMO level facilitates more efficient electron transfer and charge carrier generation, corresponding to the observed higher doping efficiency and conductivity. Our data suggest that polymers with LUMO levels below −4.3 eV exhibit substantially enhanced resistance to oxidative degradation by air. These results highlight the pivotal role of the LUMO energy level in determining the doping characteristics of n-type conjugated polymers and offer insights to further the development of high-performance, air-stable n-doped conjugated polymers.