| Particle free inks have wide application prospect in the field of printed electronics due to its advantages of low heating temperature,high printing resolution and high stability,etc.At the same time,particle free ink will greatly promote electrical industry,especially in the development of microelectronics of our country.However,there are still many issues and shortcomings on the development of particle free inks.The theoretical basis for the preparation high-performance particle free inks is unclear.The thermal decomposition process of metal inks and the evolution of microstructure of printed films are not well understood.The types of particle free ink are quite limited and the studies of all-printed devices are in the exploration stage.In this paper,particle free Ag,Cu and ZnO inks were prepared by complexing metal precusor with organic amine in organic solvent.The properties of all the inks and prepared films were characterized by using DSC?XRD?FTIR?SEM?TEM?XPS?PL?four probes and other test methods.The results of investigation provided promising ink formulations,reliable preparation processes and theoretical basis for the development of particle free inks in the field of printed electronics.For the first time,silver oxalate(Ag-Ox),with the highest Ag mass fraction in silver carboxylate was chosen as the precursor to synthesize particle free Ag ink.A paticle free Ag ink with Ag mass fraction up to 27.6 wt%was prepared.The "coffee ring" effect of the ink in inkjet printing patterns was improved by adding assistant agent to the ink.The thermal temperature of ink,microstructure and porosity of film were seriously influenced by component of amine.After changing the molar fraction of the two complexing agents,the size,morphology,distribution and contact area between each particle of the Ag particles in the film were adjusted,and the porosity and resistivity were decreased.The resistivity of films heated at 130,150 and 200? were 14.7,8.3 and 3.5 ??·cm,respectively.The effects of different organic amine species,organic amine alkyl carbon chain length,organic amine concentration on thermal decomposition temperature of ink,microstructure and electrical resistivity of the film were investigated.The mechanism of the influence of organic amine on the microstructure evolution of the film was investigated.For the inks in thermal decomposition,the existence of liquid organic amine in the film was the most important factor affecting the microstructure of the film.In the absence of organic amine,the formed silver film was composed of many separated spherical "nano silver particle clusters" and a large number of pores.In the presence of an organic amine,the uniform silver film within closely packed silver particles was formed.The effects of the types of silver carboxylate and silver carboxylate carbon chain length on the thermal decomposition temperature of the inks,microstructure and electrical resistivity of the films were studied.The thermal decomposition temperatures of Ag-Ox and silver malonate(Ag-Ma)were much lower than those of the other samples.The mechanisms of microstructure evolution of two silver carboxylates inks were investigated.The decomposition process of Ag-Ox ink was fast,forming a nearly sphere nano Ag particle with a narrow particle size.While the decomposition process of Ag-Ma ink was slow,formed various sizes Ag nano plate(hexagon,triangle).Different mole fractions Ag-Ox and Ag-Ma precursors were mixed,and the thermal decomposition process of the ink was adjusted.Therefore,the morphology,size and distribution of the particles in the film were changed.The resistivity of Ag film was only 2.5 ??·cm after heated at 130? for 30 min,corresponding to 1.5 times of the theoretical value of bulk Ag.The film showed excellent bending property.Particle free Cu ink was synthesized by using CuH2C2O4·4H2O as precursor,1,2-diaminopropane(PDA)as a complxing agent,ethanol(EtOH)as solvent.Conductive Cu film was obtained by heating the particle free ink in air.PDA was the key component of the anti-oxidiation of particle free Cu ink heated in air.As a complexing agent,PDA not only lowered the thermal decomposition temperature of Cu precursor,bu also increased the solubility of the Cu precursor in ethanol.As a reactant,PDA reacted with O2 to form imine.The Cu generated during the decomposition of the ink was used as a catalyst to isolate the O2 molecule on the surface of the metal Cu,thereby preventing oxidation of the Cu film.The Cu film heated at 180 0 C for 1 min showed the lowest resistivity of 18 ??·cm.Particle free ZnO ink was prepared by using Zn(CH3COO)2·2H2O as precursor,PDA as a complexing agent,EtOH as solvent,ethyl cellulose as assistant agent,and the molar ratios of Zn2+/-NH2 was 1:6.ZnO films were prepared by multilayer inkjet printing and inkjet printing seed layer by combined with hydrothermal method,respectively.After changing the ink concentration,heating temperature,heating time,seed layer thickness,heating temperature of seed layer and hydrothermal temperature,the ZnO thin films with c-axis preferred orientation,high crystallinity,closely contact particles,dense microstructure and ZnO nanorods array with strong c-axis preferred orientation,uniform nanorods size,good compactness,high verticality were prepared.UV detector was prepared via all-inkjet-printing technique by using synthesized particle-free ink.The detector switching ratio and photocurrent of the detector fabricated by inkjet printing seed layer combined with the hydrothermal method were larger than those of the multi-layer inkjet printing method.The switching ratio of former detector was up to 7472.The nonlinearly increasing ?-? curve indicated schottky contact was formed between Ag electrode and ZnO thin film layer.The schotty contact promoted the switching ratio and response rate much higher than that of prepared comparative Cu-ZnO-Cu detector.Bending the detectors to 45,90 and 135° for 200 times,the ?-? curves of the detector after bending were basically coincident.The detector had excellent bending property. |
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