Effect of the air humidity on the chlorine treatment for CdTe thin films solar cells. (June 2022)

• Record Type: Journal Article
• Authors: López-Sánchez, A.; Rimmaudo, I.; Mis-Fernández, R.; Camacho-Espinosa, E.; Peña, J.L.
• Is Part Of: Solar energy. Volume 239(2022)
• Page Start: 129
• Page End: 138
• Publication Date: 2022-06
• Subjects: Solar cells -- CdTe -- Chlorine treatment -- Air relative humidity -- CdCl2 -- CHClF2; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2022.04.063
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: The influence of the air relative humidity on the CdTe activation process has never been addressed. The air humidity contained in the activation atmosphere could have beneficial or detrimental effects, depending on its level and the activation chlorine compound (i.e., CHClF2 and CdCl2 ). The activation homogeneity on the sample area is compromised by the excess of humidity during the activation process. The humidity threshold for CdCl2 was found. Precise control of the air relative humidity in the activation process may be the key to achieving high solar-cell efficiencies. Abstract: Chlorine treatment is considered one of the most important processes to obtain high-efficiency CdTe solar cells. Such treatments are usually performed by exposing the devices to CdCl2 or other chlorine compounds and annealing them at high temperatures. Annealing processes were carried out in vacuum, inert atmosphere, reactive atmosphere, or air. The usage of ambient air has several advantages either technical or economical. However, the presence of moisture in the atmosphere may affect the treatment results or their reproducibility, especially in countries where the relative humidity (RH%) of the air could be an issue. However, despite many reports on CdTe Cl-treatments, the RH% effect on the finished solar-cell performance was not extensively reported. In this work, RH% was varied from 0% to 60%, comparing two different Cl treatments: CHClF2 (gas) and CdCl2 (in MeOH solution). It was observed that the RH% negatively affects the electrical properties of CHClF2 -treated solar cells, while it could reduce the spatial uniformity using CdCl2 . We conclude that relative air humidity is a parameter that should be controlled for producing high-quality CdTe-based PV devices.