Next-generation sensitizers for dye sensitizer solar cells: Molecular engineering, performance metrics, and photostability

• DSSC’s working principles and charge transport mechanisms are reviewed. • Discusses various components of DSSC and advances in dye materials. • Comprehensive analysis of dye sensitizers as light-harvesting component in DSSCs. • Examines strategies to enhance dye efficiency and stability. • Outlines key challenges and future directions in DSSC research. Dye-sensitized solar cells (DSSCs) constitute a promising class of third-generation photovoltaic devices characterized by cost-effective fabrication, semi-transparency, and efficient operation under solar illumination. At the core of their photoelectrochemical functionality lies the dye sensitizer, which plays a critical role in dictating photon absorption, interfacial electron injection, and the dynamics of charge separation and recombination. This review presents a comprehensive and mechanistic analysis of recent developments in the molecular engineering of sensitizers, with emphasis on donor–π–acceptor (D–π–A) systems, electronic conjugation strategies, anchoring group optimization, and structural modifications that enhance spectral coverage and energy level alignment with the conduction band of a wide-bandgap semiconductor such as TiO 2 . The performance of conventional ruthenium-based complexes is systematically compared to emerging classes of sensitizers, including metal-free organic dyes, porphyrinoid derivatives, quantum dots, and bio-derived chromophores. Structure–property relationships are elucidated in the context of their impact on photovoltaic parameters such as short-circuit current density (J sc ), open-circuit voltage (V oc ), fill factor (FF), and power conversion efficiency (PCE). Particular attention is given to photostability, with a detailed assessment of degradation mechanisms under thermal, photochemical, and electrochemical stress, as well as molecular and interfacial engineering strategies aimed at improving operational durability. The review further discusses current trends and future perspectives, including co-sensitization approaches, sensitizer design for low-intensity illumination environments, integration with solid-state electrolytes, and computational methods for rational dye screening. Collectively, these insights establish a roadmap for the development of next-generation sensitizers with enhanced efficiency, stability, and applicability in scalable DSSC technologies.