Polymer stabilized ZnO nanoparticles for low-temperature and solution-processed field-effect transistors

Abstract

Homogeneous, smooth and densely-packed nanoparticulate ZnO films for field-effect transistors (FETs) are formed by spin-coating suspensions of ZnO nanoparticles in an organic solvent, followed by baking at 150 C. The morphology of the films is strongly dependent on the type and amount of surfactant polymers that are employed to cap ZnO nanoparticles and stabilize the suspensions. Infrared spectroscopy, atomic force microscopy, electron microscopy and electrical characterization reveal that a certain amount of surfactant is needed to make the size of the agglomerates small enough to form such nanoparticulate films; however, an excess amount of surfactant results in an increase in the resistivity of the nanoparticulate films owing to the electrically semi-insulating nature of the surfactants. FETs composed of the nanoparticulate ZnO films in the bottom gate configuration operate in the n-channel enhancement mode with a clear saturation current at higher drain voltages. The field-effect mobility of the FETs varies by more than three orders of magnitude dependent on the type and amount of surfactants, exhibiting the highest value of 8 Â 10 À3 cm 2 V À1 s À1 . This clearly indicates that the appropriate development and synthesis of surfactants for inorganic nanocrystal suspensions are highly important for low-temperature and solution-processed FETs, compatible with plastic substrates, towards printable electronics.

Solution-processed ZnO nanoparticle-based transistors via a room-temperature photochemical conversion process

“…10 To this end, additives and dispersing aids are commonly used to assure the quality and stability of NP inks, starting from ligand shells directly attached to the particles 11 to counter ions 12 and longer carbon/polymer chains added in the dispersing medium. 13 Although these approaches ensure simple processing, they are usually introducing a large amount of electrically insulating materials that acts as energy barriers to electron transport between adjacent NPs. Hence removal of such additives and simultaneous improvement of interparticle electrical connectivity is required to increase the device performance.…”

Low‐Temperature Processing of Printed Field‐Effect Transistors from Sublimating‐Stabilizer Derived Oxide Nanodispersions

“…Whereas, the thymol‐stabilized nanodispersions are found to be stable (as shown in Figure a) and printable for about two weeks. The superior success with thymol may be associated to its hydroxyl functional groups (OH), which often adsorbs more efficiently on oxide surface and assist in stabilization. On the other hand, the agglomerate size in the nanoink has been found to be a function of the nanodispersion preparation time.…”

“…However, at the downside, these surfactant molecules, being nonconducting/semi‐insulating in nature, introduce a barrier for the interparticle charge transport, and hence would again require a postannealing step, at sufficiently high temperatures to eliminate them. The detrimental effect of the insulating ligands on the electronic transport, when allowed to remain within the semiconductor films, can be noticed in the report by Okamura et al, where an annealing at 150 °C has not been sufficient to remove the commercial stabilizer, TEGO Dispers 752 W (Evonik), from the zinc oxide (ZnO) nanoparticle surfaces, resulting in a very low mobility value of only 8 × 10 −3 cm 2 V −1 s −1 . In contrast, a nearly complete removal of stabilizers have been achieved, at room temperature, by Baby et al, by following a technique termed as chemical curing .…”

Simulation Study of Nanoparticle–Polymer Organic Suspension Stability

“…Nanoparticle suspensions are an important area of research for photoluminescence, catalysis, electronics, and optics . Among these systems, nanoparticle and dissolved polymer co‐suspensions are of most interest.…”