Stable n-type organic small-molecule conductor enabled by chemically doped ternary components

Abstract

Chemical doping is a versatile way to tune optoelectronic properties in organic semiconductors (OSCs). In comparison with p-type doping, achieving stable and efficient n-type doping in OSCs especially in small molecules remains a great challenge. The lack of universal doping strategy and OSCs with deep the lowest unoccupied molecular orbital (LUMO) energy levels and high electron mobility limit the development of n-type doped OSCs. In this work, a ternary system containing small-molecule OSC, 2DQTT-o with deep LUMO and high electron mobility, n-type dopant, N-DMBI, and polar insulating polymer, PEO were developed. With the introduction of PEO, both the miscibility, doping level and doping stabilities were significantly improved. Notably, the ternary doped components showed excellent air stability and kept 82% of the initial electrical conductivity when exposure to air for 240 h, which improved 32% in comparison with that without PEO. Furthermore, the ternary doped films also exhibited good thermal stability, retaining 55% of the initial value after heating at 200 °C. In contrast, the two-component doped films decomposed and became insulating.