Phenothiazine-based dyes for efficient dye-sensitized solar cells

As an emerging photovoltaic technology, dye-sensitized solar cells (DSSCs) have attracted a great deal of academic and industrial interest due to their reasonably high power conversion efficiency, low material cost and facile fabrication process. Metal-free organic dyes, as one of the key components of DSSCs, play a pivotal role in light harvesting and electron injection. Among the various species of organic dyes, easily tunable 10 H -phenothiazine-based dyes hold a large proportion. The electron-rich nitrogen and sulfur atoms render 10 H -phenothiazine a stronger donor character than other amines, even better than triphenylamine, tetrahydroquinoline, carbazole and iminodibenzyl. On the other hand, the unique non-planar butterfly conformation of the 10 H -phenothiazine ring can sufficiently suppress molecular aggregation and the formation of excimers. The positions N-10, C-3 and C-7 of the 10 H -phenothiazine ring system can easily be furnished with electron-donating or electron-withdrawing groups. Thus, the structural features of 10 H -phenothiazine-based dyes guarantee the fabrication of efficient DSSCs. Some 10 H -phenothiazine-based dyes show high photovoltaic performance, even better than the commercial ruthenium complex ( N719 ). This paper reviews the recent significant scientific progress in 10 H -phenothiazine-based DSSCs and focuses especially on the relationship between the molecular structure and the photoelectric conversion properties. Due to their structure features, 10 H -phenothiazine-based dyes show high photovoltaic performance and have great potential for future technical applications in dye-sensitized solar cells (DSSCs). The recent significant scientific progress of the dyes and their DSSCs is reviewed, and the relationship between the molecular structure and the photoelectric conversion properties is especially discussed.