Examining the role of ultra-thin atomic layer deposited metal oxide barrier layers on CdTe/ITO interface stability during the fabrication of solution processed nanocrystalline solar cells

• Published in: Solar energy materials and solar cells Vol. 125; pp. 164 - 169
• Main Authors: Chambers, Benjamin A., MacDonald, Brandon I., Ionescu, Mihail, Deslandes, Alec, Quinton, Jamie S., Jasieniak, Jacek J., Andersson, Gunther G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-06-2014; Elsevier
• Subjects: Annealing; Applied sciences; Cadmium tellurides; CdTe; Deposition; Devices; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Interdiffusion; Interface; Nanoparticle; Natural energy; Photoelectric conversion; Photovoltaic cells; Photovoltaic conversion; Solar cell; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Solution-processed; Titanium dioxide; Solar cell; Nanoparticle; CdTe; Interface; Solution-processed; Performance evaluation; Binary compound; Barrier layer; Doping; Annealing temperature; Interdiffusion; Thin film; Zirconium oxide; Tin addition; Thin film cell; Cadmium tellurides; n type semiconductor; Zinc oxide; Chemical composition; ITO layers; Thermal annealing; Cost lowering; Growth from solution; Nanocrystal; Ultrathin films; Oxide layer; Indium oxide; Rutherford backscattering; Manufacturing process; Diffusion barrier; Titanium oxide; Alumina; Comparative study
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2014.02.018

Solution processed CdTe layers are a potentially low-cost alternative for use in thin-film solar cells. We have recently reported the use of such nanocrystalline layers within ITO/CdTe/ZnO/Al device architectures. One key concern with this type of device structure is the possibility of atomic scale interdiffusion between the ITO and CdTe layers, which can result in deleterious n-type doping of the CdTe layer. Rutherford Backscattering has been used to study the chemical composition across the ITO/CdTe interface as a function of thermal annealing temperature. Through these measurements we verify that interdiffusion is observed across the interface for annealing temperatures above 200°C, and the extent of interdiffusion increases with temperature. Ultra-thin alumina, zirconia and titania layers deposited between the ITO and CdTe layers have been studied for their potential to act as a diffusion barrier. All investigated barriers successfully suppress interdiffusion. The outcomes of these compositional studies are directly compared to solar cells fabricated under analogous processing conditions, demonstrating improved cell performance.
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•Solution processed CdTe solar cells show diffusion across the CdTe/ITO interface.•Diffusion across the interface is detrimental for the performance of the solar cells.•Metal oxide buffer layers at the CdTe/ITO interface eliminate diffusion.•Metal oxide buffer layers at the CdTe/ITO interface improve performance.