DSSCs

Dye-sensitized solar cells (DSSCs) are a class of thin-film photovoltaic devices that convert light to electricity using a photosensitizing dye attached to a wide-bandgap semiconductor, typically titanium dioxide. When the dye absorbs photons, it injects an electron into the conduction band of the semiconductor, and the electron travels through the porous semiconductor to the conducting substrate, completing the circuit through an external load.

A typical DSSC stack consists of a transparent conducting oxide glass substrate, a mesoporous TiO2 layer coated with the dye, an electrolyte that contains a redox mediator to regenerate the dye after electron transfer, and a counter electrode that completes the electrochemical circuit. The electrolyte often contains iodide/triiodide or alternative redox couples, and the system can be liquid, quasi-solid, or solid-state depending on the electrolyte formulation.

History and development: DSSCs were first demonstrated in the early 1990s, with the Grätzel group introducing the concept that ordinary dyes and porous oxide films could achieve efficient light harvesting. Since then, improvements in dye chemistry, semiconductor films, and redox mediators have expanded the range of performance and stability, including dye-sensitized solar cells that operate under indoor lighting and flexible substrates.

Materials and performance: common dyes include ruthenium complexes and various organic dyes; TiO2 is the most widely used semiconductor. Laboratory devices have surpassed about 13–14% efficiency under standard illumination, while commercial or semi-commercial implementations typically report lower values. advantages of DSSCs include low-temperature processing, color tunability, and good performance under diffuse or indoor light; limitations center on long-term stability and sealing with liquid electrolytes. DSSCs remain an active area of research for low-cost, flexible, and semi-transparent photovoltaic applications.