Present status and future prospects for development of non- or reduced-indium transparent conducting oxide thin films

Impurity-doped ZnO Thin Films Prepared by Physical Deposition Methods Appropriate for Transparent Electrode Applications in Thin-film Solar Cells

“…In GZO and AZO films prepared by different MSDs, any differences found concerning the influence of the deposition method used on the obtained electrical properties were mainly related to differences in the impurity content doped into the films, i.e., the obtained carrier concentration. Table 1 summarizes the obtained electrical properties and the doped impurity content in AZO and GZO thin films prepared with high deposition rates and a thickness of 500 or 2000 nm on glass substrates at 200 o C by dc-MSD or rf+dc-MSD using an AZO or GZO target with an Al 2 O 3 content of 2 wt.% or a Ga 2 O 3 content of 5.7 wt.%, respectively, resulting in the lowest resistivity as well as the most suitable for transparent electrode applications in FPDs attainable [1,2,[5][6][7][8]. In contrast, an optimal B content doped into transparent conducting BZO thin films that can obtain the lowest resistivity may be not satisfactorily decided yet.…”

“…Recently, highly transparent and conductive impurity-doped ZnO thin films such as Al-and Ga-doped ZnO (AZO and GZO) prepared by magnetron sputtering depositions (MSDs) have been attracting much attention as alternatives to the indium-tin-oxide transparent electrodes used in flat panel displays (FPDs) such as liquid crystal and organic electroluminescent displays [1][2][3][4]. For such applications, it is necessary that lower resistivity AZO and GZO thin films be prepared with a thickness below approximately 200 nm on substrates at a temperature below approximately 200 o C. The lower resistivity can be achieved in AZO and GZO thin films by doping the impurities with an Al content (Al/(Al+Zn) atomic ratio) of 2-4 at.% and a Ga content (Ga/(Ga+Zn) atomic ratio) of 5-8 at.%, irrespective of the deposition method used [1,2,[5][6][7][8].…”

“…For such applications, it is necessary that lower resistivity AZO and GZO thin films be prepared with a thickness below approximately 200 nm on substrates at a temperature below approximately 200 o C. The lower resistivity can be achieved in AZO and GZO thin films by doping the impurities with an Al content (Al/(Al+Zn) atomic ratio) of 2-4 at.% and a Ga content (Ga/(Ga+Zn) atomic ratio) of 5-8 at.%, irrespective of the deposition method used [1,2,[5][6][7][8]. At the present time, AZO and B-doped ZnO (BZO) thin films are in practical use for transparent electrode applications in CuIn 1-X Ga X Se 2 -based thin-film solar cells [9][10][11][12].…”

“…This suggests that the lower resistivity AZO and GZO thin films that were developed for transparent electrode applications in FPDs, as described above, may not be appropriate for transparent electrode applications in thin-film solar cells. In addition, it is known that the electrical and structural properties obtainable in polycrystalline impurity-doped ZnO thin films are considerably affected by the deposition conditions and method used [1,7,8,26,27].…”

Improved electrical transport in Al-doped zinc oxide by thermal treatment

“…The research on TCO materials is driven by the wide range of possible applications of TCO films in many optoelectronic devices. [1][2][3] Among the various applications, thin film photovoltaics is a main driver for material research and deposition process development of TCO materials.…”