Transparent conductive oxides in flexible perovskite solar cells – material properties and device performance review

Abstract

Flexible perovskite solar cells (FPSCs) are promising alternatives to conventional solar cells, particularly for wearable and portable electronic applications that require flexible and lightweight energy sources. The integration of a transparent conductive oxide (TCO) layer is essential to achieve both conductivity and transparency. However, this requirement poses significant challenges related to flexibility, durability, and cost-effectiveness, thereby impeding commercialisation. This study aims to critically assess the limitations of commonly employed TCOs, including aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), indium tin oxide (ITO), and gallium-doped zinc oxide (GZO), focusing on their performance in FPSCs. To address the primary challenges of scalability, material costs, environmental degradation, and mechanical integrity, this review synthesises the evaluations of TCO material properties from the existing literature. These findings indicate that indium tin oxide (ITO) remains the most prevalent TCO in the field, owing to its superior optical transparency and electrical conductivity. In contrast, materials such as gallium-doped zinc oxide (GZO) and aluminum-doped zinc oxide (AZO) offer enhanced flexibility, but at the cost of reduced conductivity. Furthermore, challenges related to the uniformity of large-area films, deposition technique methodologies, and uniformity of interfaces between TCOs and charge-transporting layers further complicate the fabrication of FPSCs. Our research identifies critical areas for further investigation and development, including low-temperature deposition techniques, improved encapsulation strategies, and evaluation of alternative TCO materials to enhance the performance and viability of FPSCs. These findings have significant policy implications and underscore the need for additional research and funding in the solar energy sector.