The study aims to enhance the durability of thin-film flexible solar cells by developing a barrier layer that will act as a protective layer against chemical etching during the manufacturing process of the solar cells. This thesis is in collaboration with a Dutch flexible solar company, HyET Solar, which uses a temporary substrate to stack all the layers of the solar cell. The main problem arises when the temporary substrate is required to be removed and replaced by transparent encapsulation. The first layer after the temporary substrate is the TCO that shows defects such as pinholes, which might allow the chemical to penetrate the device and degrade it. The proposed solution is the fabrication of a barrier layer that is deposited before TCO to protect the cell stack from the etching process. Barrier layers were deposited using a scalable, industry-compatible technique, and their performance was assessed through a systematic evaluation of etch resistance and optical transparency. This was followed by optimisation of layer parameters. The findings demonstrate that properly engineered barrier layers can effectively resist chemical etching while maintaining high transparency, thereby enabling their seamless integration into flexible solar modules.