Dye-sensitized solar cells: recent advances in materials, electron transfer mechanisms, sensitizer engineering, and future directions

Abstract

Dye-sensitized solar cells (DSSCs) have attracted considerable attention as low-cost, solution-processable photovoltaic devices in which a photosensitizer adsorbed on a wide-band-gap semiconductor harvests sunlight and injects electrons into the semiconductor conduction band. The performance of a DSSC is therefore strongly governed by the optical absorption, energy-level alignment, electron-injection kinetics, regeneration efficiency, and stability of the sensitizer. This review summarizes recent advances in both metal-based and metal-free sensitizers for DSSCs, with emphasis on ruthenium polypyridyl complexes and organic donor–π–acceptor (D–π–A) dyes. The roles of anchoring groups, π-conjugated spacers, donor/acceptor engineering, aggregation suppression, and co-sensitization strategies are discussed in relation to photocurrent generation, open-circuit voltage, charge recombination, and overall power-conversion efficiency. The review also highlights the use of computational approaches, particularly time-dependent density functional theory (TD-DFT), to guide the rational design of next-generation sensitizers. Finally, key challenges and opportunities for improving efficiency, long-term stability, sustainability, and scalability of DSSC sensitizers are outlined.