Sun, B., Hong, W., Thibau, E. S., Aziz, H., Lu, Z.-H., & Li, Y. (2015). Polyethylenimine (PEI) as an effective dopant to conveniently convert ambipolar and p-type polymers into unipolar n-type polymers ACS Applied Materials \& Interfaces, 7, 18662\textendash18671.