Aggregation induced light harvesting of molecularly engineered D-A-π-A carbazole dyes for dye-sensitized solar cells. (1st November 2018) - Hemavathi, B.
Graphical abstract: Highlights: Dyes with cyanopyridine auxiliary acceptor were synthesized. J-aggregation leads to broader absorption spectra. Aggregation assisted in better performance. Abstract: Novel class of metal free organic dyes (CCTh andCCBz ) with D-A-π-A configuration, having carbazole as donor and 3-cyanopyridine as auxiliary acceptor replacing conventional benzannulated heterocycles along with variable π-linkers were synthesized and used in dye-sensitized solar cells (DSSCs). Both the dyes are having cyanoacrylic acid as the anchoring group with thiophene (CCTh ) and phenylene (CCBz ) as π-linkers. The photophysical, electrochemical, theoretical and photovoltaic properties of the dyes were investigated in detail. The absorption spectra of dyes on TiO2 showed broader absorption band forCCTh in comparison to the solution spectra indicating aggregation in solid state. The aggregation studies in varied THF/water fraction indicates J -aggregation for both the dyes.CCTh with thiophene linker showed broader absorption compared toCCBz, and the photovoltaic performance recorded forCCTh directly indicates better light harvesting ability corresponding to the red shifted J- aggregated states. Hence, solar cells fabricated withCCTh gave a power conversion efficiency of 3.39% andCCBz delivered an efficiency of 2.03% under full sun condition. A detailed investigation of device dynamics have been carried out employing charge extraction (CE), intensity-modulated photovoltage spectroscopy (IMVS) and open-circuit voltage decay (OCVD) measurements.