Metal oxide (MO) semiconductor thin films prepared from solution typically require multiple hours of thermal annealing to achieve optimal lattice densification, efficient charge transport, and stable device operation, presenting a major barrier to roll-to-roll manufacturing. Here, we report a highly efficient, cofuel-assisted scalable combustion blade-coating (CBC) process for MO film growth, which involves introducing both a fluorinated fuel and a preannealing step to remove deleterious organic contaminants and promote complete combustion. Ultrafast reaction and metal–oxygen–metal (M-O-M) lattice condensation then occur within 10–60 s at 200–350 °C for representative MO semiconductor [indium oxide (In2O3), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO)] and dielectric [aluminum oxide (Al2O3)] films. Thus, wafer-scale CBC fabrication of IGZO-Al2O3 thin-film transistors (TFTs) (60-s annealing) with field-effect mobilities as high as ∼25 cm2 V−1 s−1 and negligible threshold voltage deterioration in a demanding 4,000-s bias stress test are realized. Combined with polymer dielectrics, the CBC-derived IGZO TFTs on polyimide substrates exhibit high flexibility when bent to a 3-mm radius, with performance bending stability over 1,000 cycles.

Anion doping of transparent amorphous metal oxide (a-MO) semiconductors is virtually unexplored but offers the possibility of creating unique optoelectronic materials owing to the chemical tuning, modified crystal structures, and unusual chargetransport properties that added anions may impart. We report here the effects of fluoride (F − ) doping by combustion synthesis, in an archetypical metal oxide semiconductor, indium oxide (In−O). Optimized fluoride-doped In−O (F:In−O) thin films are characterized in depth by grazing incidence X-ray diffraction, X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure (EXAFS). Charge-transport properties are investigated in thin-film transistors (TFTs), revealing that increasing fluoride content (0.0 → 1.57 atom %) slightly lowers the on-current (I on ) and electron mobility due to scattering from loosely bound F − centers but enhances important TFT performance parameters such as the I on /I off ratio, subthreshold swing, and bias stress stability, yielding superior TFT switching versus undoped In−O. These results are convincingly explained by ab initio molecular dynamics simulations and density functional theory electronic structure calculations. Combined with the EXAFS data, the experimental and theoretical results show that F − hinders crystallization by enhancing the local and medium-range disorder, promotes a uniform film morphology, and favors the formation of deeper, more localized trap states as compared to F − -free In−O. These data also show that the local organization and electronic structure of amorphous F − -doped oxide semiconductors are significantly different from those of F − -doped crystalline oxide semiconductors and suggest new avenues to further modify a-MOs for enhanced optoelectronic properties.

A series of four donor–acceptor conjugated copolymers P1–P4 with linear and branched side chains based on a ladder-type indacenodithiazole (IDTz) moiety containing an electron-deficient thiazole unit are copolymerized with di-2-thienyl-2,1,3-benzothiadiazole (DTBT) and 4,7-di­(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazole (DTBTff) as building blocks. Their optical, electrochemical, and thermal properties and charge transport behavior in organic field-effect transistors (OFETs) are studied. All copolymers exhibit nearly identical features in solution with good solubility. In the solid state, P1 does not exhibit a significant shift, while P3 shows a 27 nm red shift, thus illustrating the influence of the side chain. In the case of copolymers P1 and P2 having linear side chains, there is a clear effect of fluorination on the film morphology, while it is less pronounced in the case of polymers P3 and P4 having branched side chains. All copolymers P1–P4 have similar highest occupied molecular orbitals regardless of fluorination, while fluorinated polymers P2 and P4 result in an increase in the lowest unoccupied molecular orbital. In addition, density functional theory calculations reveal that the energy levels of IDTz are down-shifted in comparison to its IDT counterpart containing an electron-rich thiophene unit. OFETs based on all copolymers exhibit ambipolar behavior; among the four copolymers, P2 having a linear dodecyl side chain exhibits remarkable transport properties with saturated hole mobility as high as 0.87 cm2 V–1 s–1, while P3 exhibits the highest electron mobility of up to 0.50 cm2 V–1 s–1. Our results set an interesting path to further utilize the electron-deficient thiazole block in semiconducting materials.

Zirconium oxide (ZrO x ) is an attractive metal oxide dielectric material for low-voltage, optically transparent, and mechanically flexible electronic applications due to the high dielectric constant (κ ∼ 14−30), negligible visible light absorption, and, as a thin film, good mechanical flexibility. In this contribution, we explore the effect of fluoride doping on structure−property−function relationships in low-temperature solutionprocessed amorphous ZrO x . Fluoride-doped zirconium oxide (F:ZrO x ) films with a fluoride content between 1.7 and 3.2 in atomic (at) % were synthesized by a combustion synthesis procedure. Irrespective of the fluoride content, grazing incidence X-ray diffraction, atomic-force microscopy, and UV−vis spectroscopy data indicate that all F:ZrO x films are amorphous, atomically smooth, and transparent in visible light. Impedance spectroscopy measurements reveal that unlike solution-processed fluoride-doped aluminum oxide (F:AlO x ), fluoride doping minimally affects the frequency-dependent capacitance instability of solution-processed F:ZrO x films. This result can be rationalized by the relatively weak Zr−F versus Zr−O bonds and the large ionic radius of Zr +4 , as corroborated by EXAFS analysis and MD simulations. Nevertheless, the performance of pentacene thin-film transistors (TFTs) with F:ZrO x gate dielectrics indicates that fluoride incorporation reduces I−V hysteresis in the transfer curves and enhances bias stress stability versus TFTs fabricated with analogous, but undoped ZrO x films as gate dielectrics, due to reduced trap density.

In this contribution, the structural and electronic effects of fluoride doping in both crystalline and amorphous indium oxides are investigated by both experimental and theoretical techniques. Pristine crystalline and amorphous fluoride-doped indium oxide (F:In–O) phases were prepared by solution-based combustion synthesis and sol–gel techniques, respectively. The chemical composition, environment, and solid-state microstructure of these materials were extensively studied with a wide array of state-of-the-art techniques such as UV–vis, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, 19F and 115In solid-state NMR, high-resolution transmission electron microscopy (HR-TEM), and extended X-ray absorption fine structure (EXAFS) as well as by density functional theory (DFT) computation combined with MD simulations. Interestingly, the UV–vis data reveal that while the band gap increases upon F–-doping in the crystalline phase, it decreases in the amorphous phase. The 19F solid-state NMR data indicate that upon fluorination, the InO3F3 environment predominates in the crystalline oxide phase, whereas the InO4F2 environment is predominant in the amorphous oxide phase. The HR-TEM data indicate that fluoride doping inhibits crystallization in both crystalline and amorphous In–O phases, a result supported by the 115In solid-state NMR, EXAFS, and DFT-MD simulation data. Thus, this study establishes fluoride as a versatile anionic agent to induce disorder in both crystalline and amorphous indium oxide matrices, while modifying the electronic properties of both, but in dissimilar ways.