Organic dianchor dyes for dye-sensitized solar cells

Abstract Dye-sensitized solar cells (DSSCs) are executable and dynamic method to convert neat and most abundant available energy resource. Organic dyes as sensitizers have found to be the important part of solar cells to govern the net performance of device. Several designs of the dyes have been exploited to achieve high power conversion efficiency (PCE) and also understand the structure-property relationship. The dianchor architecture is provocative and emerging as an efficacious strategy to produce structural varieties of dyes. These structures are able to enhance the light-harvesting capabilities as compared to that of monoanchor dyes due to enhanced π-conjugation and also more effectively binding on semiconductor surface to produce the higher electron collection efficiency. Most of such structures are prone to reduce self-aggregation due to bulkier molecular design that is also able to prevent electrolyte-semiconductor interaction and thus inhibit the dark-current. These fascinating properties collectively triggered to generate higher PCEs over monoanchor congener. This article provides a comprehensive review of the recent progress on the dianchor dyes, discussing the several classes of dye-designs and thus tuning the performance of the dye-sensitized solar cells. Two major classes are inaugurated as flexible geometry and fixed geometry, which are further categorized into different sub-classes. The flexible geometry has six sub-classes in which two D-π-A chromophores are connected via a π-unit or σ-unit at the donor (D) part; linked via a π-unit or σ-unit at the π-spacer part; donor-acceptor backbone directly linked at the π-linker; and different π-acceptor units shared a common arylamine-based donor part. Fixed geometry is divided into two sub-classes, first sub-class comprises two π-acceptor units linked by a single donor (oligothiophene, carbazole, porphyrin or any other π-conjugated core) while in another class, the two D-π-A segments interconnected by a saturated carbon into a spiro linkage.