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

Colloidal oleic acid (OA) capped indium oxide nanocrystal (In 2 O 3 NC) was synthesized by the hot injection method. Afterwards, the ligand exchange reaction between OA and nitrosyl tetrafluoroborate (NOBF 4 ) afforded tetrafluoroborate‐capped indium oxide nanocrystals (In 2 O 3 ‐BF 4 − NCs). In 2 O 3 ‐BF 4 − 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 cm 2 /V/s for low‐temperature annealed In 2 O 3 ‐BF 4 − NCs films at 80, 150, and 250 °C, respectively. An even higher mobility of 13.0 cm 2 /V/s was obtained by annealing the films at 350 °C, because of decreasing distance between the adjacent In 2 O 3 NCs, enhancing the electronic coupling between the neighboring NCs on the NC film by the decomposition of inorganic ligand NOBF 4 . The temperature‐dependent behavior of the electron transport of In 2 O 3 ‐BF 4 − 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 In 2 O 3 NC solid in the range from 223 to 323 K, and the activation energy decreases with increasing annealing temperatures.