In-Line Sputtered Gallium and Aluminum Codoped Zinc Oxide Films for Organic Solar Cells

Abstract

Gallium and aluminum codoped zinc oxide (GAZO) films were deposited at different temperatures by in-line sputtering. Aluminum is thermally unstable compared to other elements in GAZO films. The grains of GAZO films increase with deposition temperature. Coalescence between grains was observed for GAZO films deposited at 250°C. The deposition temperature exhibits positive influence on crystallinity, and electrical and optical properties of GAZO films. The carrier concentration and mobility of GAZO films increase, while the electrical resistivity of GAZO films decreases with deposition temperature. The average optical transmittance of GAZO films rises with deposition temperature. In-line sputtering demonstrates a potential method with simplicity, mass production, and large-area deposition to produce GAZO films with good electrical and optical quality. The electrical resistivity of 4.3×10−4 Ω cm and the average optical transmittance in the visible range from 400 to 800 nm of 92% can be obtained for GAZO films deposited at 250°C. The hybrid organic solar cells (OSC) were fabricated on GAZO-coated glass substrates. Blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were the photoactive materials in OSC. The power conversion efficiency of OSC is 0.65% for the OSC with the 250°C deposited GAZO electrode.

Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

“…Few reports were found using GAZO films as the electrode of OPV devices. Before, our group applied the as-deposited GAZO films as the electrode of OPV devices when the GAZO films were deposited at 250°C [ 27 ]. The as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO films were used as the electrode to replace ITO in fabricating hybrid OPV devices in this work.…”

Influence of Processing Time in Hydrogen Plasma to Prepare Gallium and Aluminum Codoped Zinc Oxide Films for Low-Emissivity Glass

“…The variation in the diffraction angle position can be attributed to the substitution of Zn 2+ ions by Al 3+ and Ga 3+ ions [21,28] and H2 occupied in the Zn-O bond center [32,33]. The (002) diffraction peaks shifted to low angles.…”

“…Post-annealing has been shown to improve the electrical and optical properties of as-deposited AZO/ITO films and reduce emissivity. In addition, our research team reported the effects of substrate temperature, vacuum annealing and hydrogen plasma annealing, respectively, on the structure and electrical and optical properties of GAZO films [28,30,31]. According to previous reports, the processing time of hydrogen plasma treatment can affect the structure of GAZO films and thus their physical properties [30,31].…”

“…By changing the preparation method of ZnO series (such as GAZO), the optical and electrical properties of the films can also be changed [21][22][23][24][25][26]. More previous studies report that H 2 plasma treatment and heat treatment can increase the electrical stability of GAZO or AZO and decrease the electrical resistivity [23][24][25][26][27][28]. The improvement in the electrical properties of GAZO or AZO thin films may due to the following reasons: (1) the substitution of Al and Ga into Zn sites in ZnO crystals, creating one more free electron, which can increase the carrier concentration and conductivity [21,22,28];…”

Electronic Structure and Optical Property Analysis of Al/Ga-Codoped ZnO through First-Principles Calculations

“…The Al dopant is easily oxidized during film growth because of its high reactivity, whereas the Ga dopant is more stable and resists oxidation [ 3 ]. In particular, the ionic and covalent radii of Ga are 0.62 and 1.26 Å, respectively, which are close to those of Zn (0.74 and 1.31 Å) [ 4 ]. Doping Ga in Al-doped ZnO (AZO) could reduce crystal deformation, resulting in higher crystallinity and enhanced electron transport [ 5 ].…”