Doping Indium Oxide Films with Amino‐Polymers of Varying Nitrogen Content Markedly Affects Charge Transport and Mechanical Flexibility

Abstract

AbstractHere, correlations between polymer structure and charge transport in solution‐processed indium oxide, In2O3:polymer blend flexible thin film transistors (TFTs) are investigated using four polymers having electron‐donating amine functionalities (polyethyleneimine (PEI), poly(allylamine), polyethyleneimine ethoxylated (PEIE), and PVP‐NH2 (PVP; poly(4‐vinylphenol)), and two PEI‐PEIE mixtures) with varied atomic amine nitrogen content (N%) of 12.6, 9.1, 6.9, 2.6, respectively. These amino‐polymers influence the semiconducting oxide film TFT electron mobilities via a delicate interplay of electron transfer/doping, charge generation/trap‐filling, film morphological/microstructural variations, which depend on the polymer structure, thermal stability, and N%, as well as the polymer content of the In2O3 precursor and the carbon residue content in In2O3. Thus, increasing the N% from 0.0% in the control PVP to 12.6% in PEI increases the electron doping capacity, the polymer content of the blend formulation, and the blend TFT field‐effect mobility. Optimal polymer incorporation invariably enhances charge transport by as much as ≈2×, leading to a maximum carrier mobility of 8.47 ± 0.73 cm2 V−1 s−1 on rigid Si/SiOx substrates and a remarkable 31.24 ± 0.41 cm2 V−1 s−1 on mechanically flexible polyimide/Au/F:AlOx substrates with Al contacts. Furthermore, all of the polymers equally enhance the mechanical durability of the corresponding In2O3:polymer blend TFTs with respect to mechanical stress.