Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids

Abstract

Modifying the surface of polycrystalline ZnO films using a monolayer of organic molecules with carboxylic acid attachment groups increases the field-effect electron mobility and zero-bias conductivity, resulting in improved transistors and transparent conductors. The improvement is consistent with the passivation of defects via covalent bonding of the carboxylic acid and is reversible by exposure to a UV-ozone lamp. The properties of the solvent used for the attachment are crucial because solvents with high acid dissociation constants (Ka) for carboxylic acids lead to high proton activities and etching of the nanometers-thick ZnO films, masking the electronic effect.

First principles investigations on the electronic structure of anchor groups on ZnO nanowires and surfaces

“…Our results confirm the experimental evidences of Ref. 65, where the saturation electron mobility in ZnO thin film FETs functionalized with stearic acid (CH 3 (CH 2 ) 16 COOH) was enhanced by about one order of magnitude. We found that the band bending and curvature of the -COOH-ZnO wire at the C-point are reduced compared to the bare NW.…”

Effect of UV-ozone process on the ZnO interlayer in the inverted organic solar cells

“…[19][20][21][22] The IOSC devices with a structure of indium tin oxide (ITO)/ZnONFs/poly(3-hexylthiophene):(6,6)-phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/molybdenum oxide (MoO 3 )/Ag were then fabricated. ITO-coated glass substrates were cleaned in an ultrasonic bath with acetone and isopropyl alcohol for 20 min each, rinsed with deionized water, and then blew-dried with nitrogen.…”

“…The electrical conductivity of the ZnONFs has been signicantly improved by suppressing the V O defects. 19,22 Thus, passivation of V O defects is in favor of enhancing the performances of the devices. Compared with these methods, UV-ozone treatment is regarded as an effective way to alter the surface states and modify the defects of ZnONFs without any additives.…”

“…In the past, researchers have attempted many methods aimed at deecting passivation, such as UV-ozone treatment, 10,11,13 atomic doping, 9,[16][17][18]23 surface modication, 19,20 and annealing treatments, 21 etc. The electrical conductivity of the ZnONFs has been signicantly improved by suppressing the V O defects.…”

Improving the efficiency of dye-sensitized solar cells by photoanode surface modifications

“…As for the acid treatment of ZnO photoanodes, although the ZnO surface is etched in the presence of acid owing to the dissolution of Zn + ions, some studies have reported improvement in the conductivity and mobility in ZnO upon acid treatment [63]. Chen et al [64] found that the efficiency of a DSSC increased from 0.7% to 1.2% after treatment of vertically aligned ZnO nanowires with HAuCl4 acid.…”