Effect of polymer crystallinity on the spatial distribution of dopant in sequentially solution-doped conjugated polymer thin films

Sequential solution doping is one of the most frequently used methods for doping conjugated polymer films. Since the spatial distribution of dopants in doped polymer films significantly influences their electrical properties, elucidating how various material parameters affect the dopant distribution in sequentially solution-doped polymer films is of great importance. This study investigates the effect of crystallinity in conjugated polymer thin films on the spatial distribution of dopants along the out-of-plane direction. The results show that higher crystallinity in polymer films leads to a more non-uniform dopant distribution, with a greater composition of dopants at the film surface compared to the bulk. This phenomenon is attributed to the crystallinity-dependent swellability of polymer films, where films with higher crystallinity exhibit lower swellability, resulting in less efficient dopant diffusion from the surface to the bulk compared to films with lower crystallinity.

Graphic abstract

This study explores how crystallinity in conjugated polymer thin films affects dopant distribution during sequential solution doping, revealing that higher crystallinity results in a more nonuniform distribution, with greater dopant compositions at the surface than in the bulk. This is due to lower swellability, which limits effective dopant diffusion from the surface to the bulk.