Fabrication of transparent and conductive Al-doped ZnO films for solar cells

Transparent conducting aluminum-doped ZnO thin films were deposited using a sol-gel process. In this study, the important deposition parameters were investigated thoroughly to determine the appropriate procedures to grow large area thin films with low resistivity and high transparency at low cost for device applications. The doping concentration of aluminum was adjusted in a range from 1 to 4 mol% by controlling the precursor concentration. The annealing temperatures for the pre-heat treatment and post-heat treatment was 250 o C and 400-600 o C, respectively. The SEM images show that Al doped and undoped ZnO films were quite uniform and compact. The XRD pattern shows that the Al doped ZnO film has poorer crystallinity than the undoped films. The crystal quality of Al doped ZnO films was improved with an increase of the annealing temperature to 600 o C. Although the structure of the aluminum doped ZnO films did not have a preferred orientation along the (002) plane, these films had high transmittance (> 87%) in the visible region. The absorption edge was observed at approximately 370 nm, and the absorption wavelength showed a blue-shift with increasing doping concentration. The ZnO films annealed at 500 o C showed the lowest resistivity at 1 mol% Al doping.

Section: )mentioning

confidence: 99%

Properties of Aluminum Doped Zinc Oxide Thin Film Prepared by Sol-gel Process

Yi¹,

Kim²,

Jung³

2010

“…그런데 인듐의 경우 매장량이 제한적이기 때문에 이를 대체하기 위한 많은 연구가 이루어지고 있으며 그 중 대표적인 것이 AZO (Aluminium Zinc Oxide)이다. 우수한 전기적, 광 학적 특성을 가지는 ITO를 대체하기 위해 Pulsed laser deposition, 1) Atomic layer deposition, 2) DC magnetron sput-tering, 3) Pulsed DC sputternig, 4,5) RF sputtering 6,7)…”

Section: 서 론unclassified

Magnetic Field Dependent Characteristics of Al-doped ZnO by High Power Impulse Magnetron Sputtering (HIPIMS)

Park¹,

Yang²,

Choi³

et al. 2010

In this study characteristics of Al-doped ZnO thin film by HIPIMS (High power impulse sputtering) are discussed. Deposition speed of HIPIMS with conventional balanced magnetic field is measured at about 3 nm/min, which is 30% of that of conventional RF sputtering process with the same working pressure. To generate additional magnetic flux and increase sputtering speed, electromagnetic coil is mounted at the back side of target. Under unbalanced magnetic flux from electromagnet with 1.5A coil current, deposition speed of AZO thin film is increased from 3 nm/min to 4.4 nm/min. This new value originates from the decline of particles near target surface due to the local magnetic flux going toward substrate from electromagnet. AZO film sputtered by HIPIMS process shows very smooth and dense film surface for which surface roughness is measured from 0.4 nm to 1 nm. There are no voids or defects in morphology of AZO films with varying of magnetic field. When coil current is increased from 0A to 1A, transmittance of AZO thin film decreases from 80% to 77%. Specific resistance is measured at about 2.9 × 10-2 Ω•cm. AZO film shows C-axis oriented structure and its grain size is calculated at about 5.3 nm, which is lower than grain size in conventional sputtering.

Fabrication of P-type Transparent Oxide Semiconductor SrCu2O2 Thin Films by RF Magnetron Sputtering

Seok¹,

Kim²,

Lee³

et al. 2010

Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped SnO 2 ) etc., which have been widely used in LCD, touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realize transparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additional prerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical bandgap more than ~3.0 eV. In this study, single-phase transparent semiconductor of SrCu 2 O 2 , which shows p-type conductivity, have been synthesized by 2-step solid state reaction at 950 o C under N 2 atmosphere, and single-phase SrCu 2 O 2 thin films of p-type TCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at 500 o C, 1% H 2 /(Ar + H 2 ) atmosphere. 3% H 2 /(Ar + H 2 ) resulted in formation of second phases. Hall measurements confirmed the p-type nature of the fabricated SrCu 2 O 2 thin films. The electrical conductivity, mobility of carrier and carrier density 5.27 × 10 −2 S/cm, 2.2 cm 2 /Vs, 1.53 × 10 17 /cm 3 a room temperature, respectively. Transmittance and optical band-gap of the SrCu 2 O 2 thin films revealed 62% at 550 nm and 3.28 eV. The electrical and optical properties of the obtained SrCu 2 O 2 thin films deposited by RF magnetron sputtering were compared with those deposited by PLD and e-beam.