Fused heterocycles possessing novel metal-free organic dyes for dye-sensitized solar cells

Abstract A series of fused heterocycles possessing novel metal free organic dyes viz., CPTAA-1 , CPTAA-2 , TCPTAA-1 and TCPTAA-2 has been designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs). Explorations on the relationship between the dye structures, photophysical/electrochemical properties, and DSSC performances have been described. The dyes CPTAA-1 and CPTAA-2 possess superior absorption maxima both in dichloromethane and adsorbed on TiO 2 compared to TCPTAA-1 and TCPTAA-2 . All the dyes display more positive ground state oxidation potential than the redox potential of I − /I 3 − electrolyte and more negative excited state oxidation potential than the conduction band edge of the semiconductor. Incorporation of additional carbazole scaffolds in CPTAA-1 and CPTAA-2 culminated with reduced photocurrent density, probably, due to poor interaction between the bulky dyes ( TCPTAA-1 and TCPTAA-2 ) and semiconductor. Of the DSSCs fabricated, the one with CPTAA-1 displayed the highest incident photon-to-current conversion efficiency (IPCE). The DSSC device with CPTAA-1 exhibited high power conversion efficiency ( η  = 4.38 ± 0.3%) compared to the others with an open circuit voltage ( V OC ) of 648 ± 0.4 mV, short circuit current density ( J SC ) of 10.03 ± 0.2 mA cm −2 , and fill factor ( ff ) of 0.66 ± 0.002 under simulated AM 1.5G irradiation (100 mW/cm −2 ).