Comparison of electrodeposited and sputtered intrinsic and aluminium-doped zinc oxide thin films

Abstract

Intrinsic zinc oxide (i-ZnO) and aluminium-doped ZnO (ZnO:Al) are components of high-efficiency copper indium gallium diselenide solar cells. This paper examines both of these materials grown by two different techniques, namely radio frequency sputtering and electrodeposition (ED) for comparison and a better understanding. X-ray diffraction showed all materials to be polycrystalline and hexagonal (wurtzite) ZnO. Scanning electron microscopy indicated crystallites with different orientations for ED materials compared to agglomerated nanocrystallites of the sputtered layers. The band-gap energy was determined to be in the range 3.27-3.45 eV. The transmission was 85% for both ED materials and 95% for the sputtered layers. Glass/FTO/i-ZnO/Al structures were rectifying, and glass/FTO/ZnO:Al/Al contacts were ohmic for both ZnO:Al layers. Addition of Al decreases the bulk resistivity for both i-ZnO layers by 1-2 orders of magnitude. The photovoltage response to pulsed illumination showed a slow relaxation hysteresis, and all materials showed n-type electrical conduction.

A comparative study on structural, optical, photoconductivity properties of In and Al doped ZnO thin films grown onto glass and FTO substrates grown by spray pyrolysis process

“…Thus, this result concorded with the best photoconductivity 400 ( cm) −1 [31] and high transmittance equals to 100% in visible range for IZO/glass [33].…”

“…The starting material used was zinc acetate dihydrated, Zn (CH3COO)2·2H2O) [30,31]. Doping sources were aluminium nitrate nonahydrated (Al (NO3)3·9H2O) and indium(III) chloride (InCl3) [11,12,30].…”

Nanocrystalline Mn and Fe Doped ZnO Thin Films Prepared Using SILAR Method for Dilute Magnetic Semiconductor Application

“…An electroless -chemical process is proposed, consisting in the formation of the super oxide radical (O cations. (Wellings et al, 2008) have deposited ZnO thin films from aqueous zinc nitrate solution at 80ºC onto fluorine doped tin oxide (FTO) coated glass substrates. Structural analysis, surface morphology, optical studies and electrical conductivity were studied and thickness of the ZnO films was found to be 0.40 μm.…”

Electrodeposition of Nanostructured ZnO Films and Their Photoelectrochemical Properties

“…The main purpose has been the preparation of transparent front contact layers in CIGS and CdTe solar cells. Higher conductivity of these layers has been achieved by incorporation of B [61,62], Al [63,64] or In [63,65] during electrodeposition of ZnO from aqueous zinc nitrate solution, by addition of dimethylamine borane, aluminum trichloride or indium nitrate to the electrodeposition bath. For moderate doping levels of 1-2%, the typical hexagonal crystal structure of ZnO is preserved in the obtained materials.…”

“…In fact, front contact layers in CIGS and CdTe solar cells are usually still made by gas-phase methods, such as electron-beam evaporation [78] or sputtering [64,79] for this reason. For the same reason, only few studies exist in which electrodeposited ZnO films have been used as a component in p-n bulk heterojunctions.…”