In and Ga Codoped ZnO Film as a Front Electrode for Thin Film Silicon Solar Cells

Abstract

Doped ZnO thin films have attracted much attention in the research community as front-contact transparent conducting electrodes in thin film silicon solar cells. The prerequisite in both low resistivity and high transmittance in visible and near-infrared region for hydrogenated microcrystalline or amorphous/microcrystalline tandem thin film silicon solar cells has promoted further improvements of this material. In this work, we propose the combination of major Ga and minor In impurities codoped in ZnO film (IGZO) to improve the film optoelectronic properties. A wide range of Ga and In contents in sputtering targets was explored to find optimum optical and electrical properties of deposited films. The results show that an appropriate combination of In and Ga atoms in ZnO material, followed by in-air thermal annealing process, can enhance the crystallization, conductivity, and transmittance of IGZO thin films, which can be well used as front-contact electrodes in thin film silicon solar cells.

On the Effect of the Co-Introduction of Al and Ga Impurities on the Electrical Performance of Transparent Conductive ZnO-Based Thin Films

“…This indicates that, with a certain combination of aluminum and gallium impurities, it is possible to achieve an even more significant enhancement in the crystallization processes of ZnO films via co-doping than those of single doping only with Ga. Similar results were noted in other studies [ 12 , 37 ]. Pham et al [ 12 ] demonstrated that the presence of a small amount of In dopants (0.1 at%), combined with mainly Ga dopants (4.9 at.%) in the ZnO target, could significantly improve the crystallization of sputtered ZnO films.…”

“…It is known that enhancing the mobility in polycrystalline thin films is often associated with an improvement in their morphology and crystallinity, diminishing defects in the lattice, or a reduction in the ionized impurity scattering inside the crystallites, thus forming a continuous film [ 12 ]. In order to gain more information about the aspects leading to the enhanced electrical performance of the co-doped 2A2GZO thin film, additional comparative investigations of the microstructure of single- and co-doped thin films deposited at the substrate temperature of 300 °C were performed.…”

“…However, for the wider use of the ZnO-based TCO films as transparent electrodes in modern optoelectronic devices, some improvements in thin films’ performance regarding their electrical properties and long-term stability are further required both by optimizing the thin-film deposition processes and by tuning the film doping. Regarding the doping optimization, if a large number of earlier studies were devoted to finding the best donor for ZnO TCO films, as well as optimizing the level of doping, an increasing number of reports have recently appeared indicating that the simultaneous co-doping of ZnO with two or more types of impurities leads to a noticeable improvement in the electrical characteristics of TCO films, as well as their microstructures [ 10 , 11 , 12 , 13 , 14 , 15 ]. In particular, we have shown that the co-doping of ZnO with Ga and B leads to the formation of denser films with an improved film microstructure and, as a result, to an increase in the thermal stability of ZnO TCO films [ 10 ].…”

Changing the thickness of two layers: i-ZnO nanorods, p-Cu2O and its influence on the carriers transport mechanism of the p-Cu2O/i-ZnO nanorods/n-IGZO heterojunction

“…The films were deposited in pure Ar gas plasma with a sputtering pressure of 0.4 Pa and power density of 1.32 W/cm 2 . The substrate temperature 300 °C and the target-substrate distance 5 cm are constant during deposition (Pham et al 2014 ). The electrical properties IGZO thin films, including carrier concentration, mobility, and resistivity are corresponding to 8 × 10 20 cm −3 , 25 cm 2 /V s and 7.5 × 10 −4 Ω cm (Fig.…”

Comparative investigation on cation-cation (Al-Sn) and cation-anion (Al-F) co-doping in RF sputtered ZnO thin films: Mechanistic insight

“…The lowest resistivity of 4×10 -3 Ω-cm has been obtained by Pan et al [34] for 1 at% Al with 2 at% Sn doped sol-gel processed thin films. A lowest resistivity of 2.5×10 −4 Ω-cm has been obtained by Pham et al in sample containing 0.1 at% In and 4.9 at% Ga [35]. A sputter deposited thin film by Lee at al.…”