Solution‐processed Tetrafluoroborate‐capped In₂O₃ Nanocrystal Thin‐Film Transistors

Abstract

Colloidal oleic acid (OA) capped indium oxide nanocrystal (In2O3 NC) was synthesized by the hot injection method. Afterwards, the ligand exchange reaction between OA and nitrosyl tetrafluoroborate (NOBF4) afforded tetrafluoroborate‐capped indium oxide nanocrystals (In2O3‐BF4− NCs). In2O3‐BF4− NCs thin‐film transistor (TFT) devices were fabricated by spin coating, exhibiting an electron mobility of 7.3 × 10−3, 5 × 10−2, and 0.19 cm2/V/s for low‐temperature annealed In2O3‐BF4− NCs films at 80, 150, and 250 °C, respectively. An even higher mobility of 13.0 cm2/V/s was obtained by annealing the films at 350 °C, because of decreasing distance between the adjacent In2O3 NCs, enhancing the electronic coupling between the neighboring NCs on the NC film by the decomposition of inorganic ligand NOBF4. The temperature‐dependent behavior of the electron transport of In2O3‐BF4− NCs films annealed at different temperatures of 150, 250, and 350 °C for application in TFT device is also reported. We conclude that thermally activating electron transport mechanism through nearest neighbor hopping works for the In2O3 NC solid in the range from 223 to 323 K, and the activation energy decreases with increasing annealing temperatures.

Electronic Coupling in π-Conjugated Molecule-Bridged Silicon Quantum Dot Clusters Synthesized by Sonogashira Cross-Coupling Reaction

“…Figure c shows two different slopes, one in the range from 133 to 193 K and the other in the range from 213 to 293 K. In addition, Figure d shows different slopes, one in the range from 133 to 193 K and the other in the range from 213 to 293 K. Here, we take the graphs and their slopes of the higher temperature range for the following two reasons. The first reason is that in the high-temperature range, the NNH process exactly matching with our Marcus-type charge transfer is favored, whereas in the lower temperature range, a variable range hopping process is preferred. , The second reason is that eq on the charge transfer rate in the classical Marcus theory has been quantum mechanically formulated in the higher temperature range, − for example, the equation is well-applied for explaining carrier mobility at room temperature in organic semiconductor thin films. , From the slope of the higher temperature plot, we can obtain the activation energy value E a,mono = 42 meV for the 4-Es/Oct Si QD thin film, which is larger than the activation energy value E a,cluster = 34 meV for the Si QD cluster thin film (Figure c–e). In other words, the reorganization energy for 4-Es/Oct Si QD and Si QD cluster thin films is calculated to be 170 and 140 meV, respectively, using eq .…”

“…The first reason is that in the high-temperature range, the NNH process exactly matching with our Marcus-type charge transfer is favored, whereas in the lower temperature range, a variable range hopping process is preferred. 33,34 The second reason is that eq 1 on the charge transfer rate in the classical Marcus theory has been quantum mechanically formulated in the higher temperature range, 35−37 for example, the equation is well-applied for explaining carrier mobility at room temperature in organic semiconductor thin films. 31,38 From the slope of the higher temperature plot, we can obtain the activation energy value E a,mono = 42 meV for the 4-Es/Oct Si QD thin film, which is larger than the activation energy value E a,cluster = 34 meV for the Si QD cluster thin film (Figure 5c–e).…”

Effect of annealing temperature and capping ligands on the electron mobility and electronic structure of indium oxide nanocrystal thin films: a comparative study with oleic acid, benzoic acid, and 4-aminobenzoic acid

“…Typically, the electron transport mechanism of the organic ligand-capped In 2 O 3 NC thin films annealed at various temperatures follows a thermally activated process that can be expressed as 43 where μ is the electron mobility, μ 0 is a temperature-independent pre-exponential factor, T is the temperature, E a is the activation energy, and k B is the Boltzmann constant. Although E a can be derived from the slope of an Arrhenius plot, we present herein a novel activation energy equation derived from our model equation for the relationship between electron mobility, activation energy, and temperature.…”

Controlling the Surface of Aluminum Nanocrystals: From Aluminum Oxide to Aluminum Fluoride

“…The small residual mass is associated with either residues of oleate molecules on the Al NCs-NOBF 4 surface, or/and with the decomposition of BF 4 − anions, passivating the surface, similar to what was observed elsewhere. [38,45]…”

“…Upon reactions of NOBF 4 with various metal‐oxides and semiconductor oleate‐coated NCs, oxide etching reactions are observed, as well as a ligand exchange reaction, in which the BF 4 − anions end up passivating the outer surface of the NCs, as inorganic ligands. [ 38,45–48 ] Although this process was successfully demonstrated on a wide range of NCs, this is the first report for its functionality on Al NCs. Hence, we studied the kinetics and mechanism of the NOBF 4 treatment, with different concentrations and incubation time intervals, providing the base data for extracting the reaction mechanism.…”