Highly transparent and conductive indium-doped zinc oxide films deposited at low substrate temperature by spray pyrolysis from water-based solutions

Abstract

In this paper, indium-doped zinc oxide (IZO) films were grown by spray pyrolysis, using zinc acetate and indium acetylacetonate precursors. The focus was on developing a solution recipe based on water as solvent, with only minor acetic acid content, as well as keeping the substrate temperature as low as possible-at 360°C. The process is therefore environment friendly and energy efficient. Despite the challenging conditions, the resulting IZO films were highly transparent and conductive. Their texture deviates strongly from the (002) texture of ZnO and depends on the indium content, which also influences the resistivity. The latter attains its minimum for an indium concentration of 4 at.% in the solution and decreases for increasing film thickness, reaching the value of (5.0 ± 0.1) 9 10 -3 X cm, mainly due to the increase in carrier mobility. The stability of the resistivity after high dose of UV irradiation was found to increase with the carrier density and the film thickness. Thick, highly doped films show minimal resistivity modification even after a total dose of 12.1 kJ/cm 2 UVA/ UVB irradiation. Finally, to demonstrate its applicability in devices, the IZO electrode was used for the fabrication of a lead-perovskite absorber solar cell, yielding an energy conversion efficiency of 6% and 910 mV open-circuit voltage.

Rapid Processing of In-Doped ZnO by Spray Pyrolysis from Environment-Friendly Precursor Solutions

“…A low HAc concentration resulted in unwanted precipitates on the film surface, while a high HAc concentration caused an increase in film resistivity. In accordance with our previous results [8], the lowest resistivity (7.4 × 10 −3 Ω·cm) combined with highest transparency (>80%) were obtained for~1500 nm-thick films deposited from a solution containing 8 vol % HAc (pH = 3.65).…”

“…Within the narrow concentration range for InAc 3 (3-5 mol %) and HAc (4-16 vol %) in this study, there was practically no obvious influence on the growth rate, as shown in Figure 1a,b. In comparison to our previous study [8], changing the zinc acetate concentration from 0.1 to 0.2 M and the type of indium precursor salt resulted in a~4-fold increase of the growth rate, as displayed in Figure 1. In Figure 1c it can be observed that increasing the deposition temperature from 360 to 400 • C resulted in a minor gradual decrease of the growth rate.…”

“…Film growth rate dependency on the (a) acetic acid concentration, (b) indium acetate concentration, (c) deposition temperature, and (d) flow rate compared to our previous results[8].…”

“…Previously, we reported on the spray pyrolysis of In-doped ZnO (IZO) films with Zn-acetate and In-acetylacetonate (In(acac) 3 ) as precursors [8]. Although the films were highly transparent and conductive, the film growth rate was restricted to~10 nm/min.…”

Investigations of the optical and electronic effects of silicon and indium co-doping on ZnO thin films deposited by spray pyrolysis

“…1.2 × 10 20 cm −3 although those films prepared from sputtering have somewhat higher values of these transport properties. In-doped ZnO (IZO) films deposited either by sputtering or spray pyrolysis have been investigated extensively [17][18][19][20][21][22][23][24][25][26] and the films produced by spray pyrolysis show conductivities of the order of 700 Ω −1 cm −1 and carrier concentrations around 3.2 × 10 20 cm −3 . We have investigated whether co-doping with both Si and In together can enable the spray deposition of films which reduce the In content whilst also maintaining the overall electrical and optical performance.…”