Magnesium-doped Zinc Oxide as a High Resistance Transparent Layer for thin film CdS/CdTe solar cells

Abstract

Magnesium-doped Zinc Oxide (MZO) was used as an alternative high resistance transparent layer for CdS/CdTe thin film solar cells. Thin films of MZO were deposited by RF magnetron sputtering and deposited on an Indium Tin Oxide contact (ITO). Thin film CdTe devices including a MZO high resistance transparent layer deposited at above 300 • C yielded a mean efficiency exceeding 10.5 %. This compares with an efficiency of 8.2 % without the MZO layer. The improvement in efficiency was due to a higher open circuit voltage and fill factor. Lowering the deposition temperature of MZO reduced the performance of the devices. Index Terms-magnesium-doped zinc oxide, high resistance transparent layer, thin film, solar cells, CdTe.

Eliminating S-Kink To Maximize the Performance of MgZnO/CdTe Solar Cells

“…9−12 Bittau et al improved their CdS/CdTe solar cell performance from 8.2% to 10.5% when ZMO was deposited prior to the CdS layer. 9 Wang et al obtained an efficiency of 13.1% and 14.7% for ZMO/CdS/CdTe and ZMO/CdS/CdSe/CdTe stack, respectively. 10 Menossi et al improved the efficiency of CdS/CdTe devices to 16.2% with ZMO as high resistive transparent layer.…”

Optical Properties of Magnesium-Zinc Oxide for Thin Film Photovoltaics

“…The most clearly observable feature in the pattern for MZO on SLG in Figure 1 is near 34°, indexed as a (002) plane diffraction, revealing that the MZO films crystallize in the hexagonal crystal system. The presence of this feature also reveals that the dominant phase for all MZO films exhibits the wurtzite crystal structure which is the stable phase of ZnO [ 19 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. With increasing Mg atomic fraction x , this (002) peak shifts to higher diffraction angle characteristic of the decrease in lattice parameter c due to the substitution of Mg at Zn lattice sites [ 29 , 30 , 31 , 33 , 34 , 36 ].…”

“…It is interesting that the largest lower limit on the crystalline size occurs for the higher x compositional range of ~0.3-0.4, corresponding to a bandgap range of 3.7-3.8 eV, suggesting a reduction in intragranular defect density The most clearly observable feature in the pattern for MZO on SLG in Figure 1 is near 34 • , indexed as a (002) plane diffraction, revealing that the MZO films crystallize in the hexagonal crystal system. The presence of this feature also reveals that the dominant phase for all MZO films exhibits the wurtzite crystal structure which is the stable phase of ZnO [19,[29][30][31][32][33][34][35][36]. With increasing Mg atomic fraction x, this (002) peak shifts to higher diffraction angle characteristic of the decrease in lattice parameter c due to the substitution of Mg at Zn lattice sites [29][30][31]33,34,36].…”

“…of ZnO [19,[29][30][31][32][33][34][35][36]. With increasing Mg atomic fraction x, this (002) peak shifts to higher diffraction angle characteristic of the decrease in lattice parameter c due to the substitution of Mg at Zn lattice sites [29][30][31]33,34,36].…”

“…Finally, it should be emphasized that in order to avoid the low crystalline quality and secondary metastable phases, a possible strategy is to adopt elevated temperatures for deposition or post-deposition annealing. This strategy was found not only to improve film structure but simultaneously to widen the MZO film bandgap [30,34,35]. Such an approach, however, adds another parameter in addition to the ZnO and MgO target power levels that would require investigation of its effect on film composition.…”